Add clarifying comment to blacken nox target.

[yoshi-automation]

This PR was generated using Autosynth. 🌈

Here's the log from Synthtool:

synthtool > Executing /tmpfs/src/git/autosynth/working_repo/websecurityscanner/synth.py.
synthtool > Ensuring dependencies.
synthtool > Pulling artman image.
latest: Pulling from googleapis/artman
Digest: sha256:5fd9aee1d82a00cebf425c8fa431f5457539562f5867ad9c54370f0ec9a7ccaa
Status: Image is up to date for googleapis/artman:latest
synthtool > Cloning googleapis.
synthtool > Running generator for google/cloud/websecurityscanner/artman_websecurityscanner_v1alpha.yaml.
synthtool > Generated code into /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/python/websecurityscanner-v1alpha.
synthtool > Copy: /home/kbuilder/.cache/synthtool/googleapis/google/cloud/websecurityscanner/v1alpha/finding_type_stats.proto to /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/python/websecurityscanner-v1alpha/google/cloud/websecurityscanner_v1alpha/proto/finding_type_stats.proto
synthtool > Copy: /home/kbuilder/.cache/synthtool/googleapis/google/cloud/websecurityscanner/v1alpha/crawled_url.proto to /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/python/websecurityscanner-v1alpha/google/cloud/websecurityscanner_v1alpha/proto/crawled_url.proto
synthtool > Copy: /home/kbuilder/.cache/synthtool/googleapis/google/cloud/websecurityscanner/v1alpha/finding.proto to /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/python/websecurityscanner-v1alpha/google/cloud/websecurityscanner_v1alpha/proto/finding.proto
synthtool > Copy: /home/kbuilder/.cache/synthtool/googleapis/google/cloud/websecurityscanner/v1alpha/finding_addon.proto to /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/python/websecurityscanner-v1alpha/google/cloud/websecurityscanner_v1alpha/proto/finding_addon.proto
synthtool > Copy: /home/kbuilder/.cache/synthtool/googleapis/google/cloud/websecurityscanner/v1alpha/scan_run.proto to /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/python/websecurityscanner-v1alpha/google/cloud/websecurityscanner_v1alpha/proto/scan_run.proto
synthtool > Copy: /home/kbuilder/.cache/synthtool/googleapis/google/cloud/websecurityscanner/v1alpha/web_security_scanner.proto to /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/python/websecurityscanner-v1alpha/google/cloud/websecurityscanner_v1alpha/proto/web_security_scanner.proto
synthtool > Copy: /home/kbuilder/.cache/synthtool/googleapis/google/cloud/websecurityscanner/v1alpha/scan_config.proto to /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/python/websecurityscanner-v1alpha/google/cloud/websecurityscanner_v1alpha/proto/scan_config.proto
synthtool > Placed proto files into /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/python/websecurityscanner-v1alpha/google/cloud/websecurityscanner_v1alpha/proto.
.coveragerc
.flake8
MANIFEST.in
noxfile.py.j2
setup.cfg
Running session blacken
Creating virtualenv using python3.6 in /tmpfs/src/git/autosynth/working_repo/websecurityscanner/.nox/blacken
pip install --upgrade black
black google tests docs
reformatted /tmpfs/src/git/autosynth/working_repo/websecurityscanner/google/cloud/websecurityscanner_v1alpha/gapic/enums.py
reformatted /tmpfs/src/git/autosynth/working_repo/websecurityscanner/google/cloud/websecurityscanner_v1alpha/gapic/transports/web_security_scanner_grpc_transport.py
reformatted /tmpfs/src/git/autosynth/working_repo/websecurityscanner/google/cloud/websecurityscanner_v1alpha/proto/crawled_url_pb2_grpc.py
reformatted /tmpfs/src/git/autosynth/working_repo/websecurityscanner/google/cloud/websecurityscanner_v1alpha/gapic/web_security_scanner_client_config.py
reformatted /tmpfs/src/git/autosynth/working_repo/websecurityscanner/google/cloud/websecurityscanner_v1alpha/proto/finding_addon_pb2_grpc.py
reformatted /tmpfs/src/git/autosynth/working_repo/websecurityscanner/google/cloud/websecurityscanner_v1alpha/proto/crawled_url_pb2.py
reformatted /tmpfs/src/git/autosynth/working_repo/websecurityscanner/google/cloud/websecurityscanner_v1alpha/proto/finding_pb2_grpc.py
reformatted /tmpfs/src/git/autosynth/working_repo/websecurityscanner/google/cloud/websecurityscanner_v1alpha/proto/finding_type_stats_pb2.py
reformatted /tmpfs/src/git/autosynth/working_repo/websecurityscanner/google/cloud/websecurityscanner_v1alpha/proto/finding_type_stats_pb2_grpc.py
reformatted /tmpfs/src/git/autosynth/working_repo/websecurityscanner/google/cloud/websecurityscanner_v1alpha/proto/finding_addon_pb2.py
reformatted /tmpfs/src/git/autosynth/working_repo/websecurityscanner/google/cloud/websecurityscanner_v1alpha/proto/scan_config_pb2_grpc.py
reformatted /tmpfs/src/git/autosynth/working_repo/websecurityscanner/google/cloud/websecurityscanner_v1alpha/proto/finding_pb2.py
reformatted /tmpfs/src/git/autosynth/working_repo/websecurityscanner/google/cloud/websecurityscanner_v1alpha/proto/scan_run_pb2_grpc.py
reformatted /tmpfs/src/git/autosynth/working_repo/websecurityscanner/google/cloud/websecurityscanner_v1alpha/gapic/web_security_scanner_client.py
reformatted /tmpfs/src/git/autosynth/working_repo/websecurityscanner/google/cloud/websecurityscanner_v1alpha/proto/scan_run_pb2.py
reformatted /tmpfs/src/git/autosynth/working_repo/websecurityscanner/google/cloud/websecurityscanner_v1alpha/proto/web_security_scanner_pb2_grpc.py
reformatted /tmpfs/src/git/autosynth/working_repo/websecurityscanner/google/cloud/websecurityscanner_v1alpha/proto/scan_config_pb2.py
reformatted /tmpfs/src/git/autosynth/working_repo/websecurityscanner/tests/unit/gapic/v1alpha/test_web_security_scanner_client_v1alpha.py
reformatted /tmpfs/src/git/autosynth/working_repo/websecurityscanner/google/cloud/websecurityscanner_v1alpha/proto/web_security_scanner_pb2.py
All done! ✨ 🍰 ✨
19 files reformatted, 9 files left unchanged.
Session blacken was successful.
synthtool > Cleaned up 2 temporary directories.
synthtool > Wrote metadata to synth.metadata.