chore: use CLOUD_JAVA_BOT_TOKEN in generate_new_client.yaml

[diegomarquezp]

Some actions are failing in commands that require github authentication
#10179 (comment)

This includes generate_new_client.yaml. In this PR I try the Cloud Java Bot Github token to check whether this is a token expiration problem

Edit: see one of the resulting PRs: #10238

[diegomarquezp]

Currently investigating:

+ gh pr create --fill --head new-library/meet-qwvU5
could not compute title or body defaults: failed to run git: fatal: ambiguous argument 'origin/main...new-library/meet-qwvU5': unknown revision or path not in the working tree.
Use '--' to separate paths from revisions, like this:
'git <command> [<revision>...] -- [<file>...]'

From https://github.com/googleapis/google-cloud-java/actions/runs/7561708004/job/20590583313

edit: Can't reproduce locally - it probably depends on some gh environment setup. My gh pr create... produced #10235, which has wrong name and description

will try a different approach to generate PR name

[suztomo]

It seems the problem is "--fill" option cli/cli#5896. If you explicitly specify title and body, it may work.

[diegomarquezp]

gh pr create --title 'feat: [meet] new module for meet' --body 'Generated with https://github.com/googleapis/google-cloud-java/actions/workflows/generate_new_client.yaml

Command used:

\```
python generation/new_client/new-client.py generate --api_shortname="meet" --proto-path="google/apps/meet" --name-pretty="Google Meet API" --product-docs="https://developers.google.com/meet/api/guides/overview" --api-description="The Google Meet REST API lets you create and manage meetings for Google Meet and offers entry points to your users directly from your app" --transport="grpc"
\```' --head new-library/meet-jcOi0
pull request create failed: GraphQL: must be a collaborator (createPullRequest)

I thought Cloud Java Bot was a collaborator, I'll check on that. We can always use ${{ github.token }} though

edit: I added it as collaborator and I could create #10237, but I'll try ${{ github.token }} to see if we can modify the author shown in the PR description

edit 2: So the author of the PR can't be set by design. I modified the PR body message to mention the author and set the token back to CLOUD_JAVA_BOT_TOKEN

[diegomarquezp]

#10238 generated by the latest run - looks OK