Bump protobuf from 3.15.0 to 3.18.3

Bumps [protobuf](https://github.com/protocolbuffers/protobuf) from 3.15.0 to 3.18.3.
- [Release notes](https://github.com/protocolbuffers/protobuf/releases)
- [Changelog](https://github.com/protocolbuffers/protobuf/blob/main/generate_changelog.py)
- [Commits](protocolbuffers/protobuf@v3.15.0...v3.18.3)

---
updated-dependencies:
- dependency-name: protobuf
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

requirements.txt

@@ -37,7 +37,7 @@ Pillow==9.0.1
 pio==0.0.3
 prometheus-client==0.8.0
 prometheus-flask-exporter==0.15.0
-protobuf==3.15.0
+protobuf==3.18.3
 pyasn1==0.4.8
 pyasn1-modules==0.2.8
 pycparser==2.20