CI hotfix: update env for protobuf

[Borda]

What does this PR do?

adding

PROTOCOL_BUFFERS_PYTHON_IMPLEMENTATION: "python"

Does your PR introduce any breaking changes? If yes, please list them.

Before submitting

• Was this discussed/approved via a GitHub issue? (not for typos and docs)
• Did you read the contributor guideline, Pull Request section?
• Did you make sure your PR does only one thing, instead of bundling different changes together?
• Did you make sure to update the documentation with your changes? (if necessary)
• Did you write any new necessary tests? (not for typos and docs)
• Did you verify new and existing tests pass locally with your changes?
• Did you list all the breaking changes introduced by this pull request?
• Did you update the CHANGELOG? (not for typos, docs, test updates, or minor internal changes/refactors)

PR review

Anyone in the community is welcome to review the PR.
Before you start reviewing, make sure you have read the review guidelines. In short, see the following bullet-list:

• Is this pull request ready for review? (if not, please submit in draft mode)
• Check that all items from Before submitting are resolved
• Make sure the title is self-explanatory and the description concisely explains the PR
• Add labels and milestones (and optionally projects) to the PR so it can be classified

Did you have fun?

Make sure you had fun coding 🙃

cc @carmocca @akihironitta @Borda

[akihironitta]

#13177 will be merged soon (hopefully), and there should be no errors related to protobuf, but do we still want this env var?

[awaelchli]

I advise against this. This could have a considerable impact on speed.

[Borda]

This could have a considerable impact on speed.

Do you mean the speed of CI or what speed?