fix(component): Use Python3.6 to build KFP launcher component

[chensun]

Post-submit build-each-commit is failing on building the KFP launcher component into Docker image:
https://pantheon.corp.google.com/cloud-build/builds/03befb37-3ff6-4283-aa1a-73dc9629ddb4;step=18?project=ml-pipeline-test

Because it uses Python 2.7 which doesn't recognize f-strings.

Installed /usr/local/lib/python2.7/dist-packages/pip-21.0-py2.7.egg
Processing dependencies for pip
Finished processing dependencies for pip
Traceback (most recent call last):
  File "/usr/local/bin/pip", line 9, in <module>
    load_entry_point('pip==21.0', 'console_scripts', 'pip')()
  File "/usr/lib/python2.7/dist-packages/pkg_resources/__init__.py", line 542, in load_entry_point
    return get_distribution(dist).load_entry_point(group, name)
  File "/usr/lib/python2.7/dist-packages/pkg_resources/__init__.py", line 2569, in load_entry_point
    return ep.load()
  File "/usr/lib/python2.7/dist-packages/pkg_resources/__init__.py", line 2229, in load
    return self.resolve()
  File "/usr/lib/python2.7/dist-packages/pkg_resources/__init__.py", line 2235, in resolve
    module = __import__(self.module_name, fromlist=['__name__'], level=0)
  File "/usr/local/lib/python2.7/dist-packages/pip-21.0-py2.7.egg/pip/_internal/cli/main.py", line 60
    sys.stderr.write(f"ERROR: {exc}")
                                   ^
SyntaxError: invalid syntax
The command '/bin/sh -c apt-get update -y &&     apt-get install --no-install-recommends -y -q ca-certificates python-dev python-setuptools wget &&     easy_install pip &&     pip install pyyaml==3.12 kubernetes' returned a non-zero code: 1

Fixes #5007

[zijianjoy]

/approve

Thank you Chen!

[numerology]

/approve

Thanks!

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: chensun, numerology, zijianjoy

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• components/kubeflow/launcher/OWNERS [numerology]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[google-oss-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: chensun, numerology, zijianjoy

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• components/kubeflow/launcher/OWNERS [numerology]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[zijianjoy]

/lgtm