[CI/Build] Automate PR body text cleanup

[russellb]

Add a github workflow that will prune tempalte text from PRs. This
will help ensure that the PR body is appropriate for inclusion in the
squashed commit when a PR is merged.

Signed-off-by: Russell Bryant rbryant@redhat.com

[github-actions]

👋 Hi! Thank you for contributing to the vLLM project.
Just a reminder: PRs would not trigger full CI run by default. Instead, it would only run fastcheck CI which starts running only a small and essential subset of CI tests to quickly catch errors. You can run other CI tests on top of those by going to your fastcheck build on Buildkite UI (linked in the PR checks section) and unblock them. If you do not have permission to unblock, ping simon-mo or khluu to add you in our Buildkite org.

Once the PR is approved and ready to go, your PR reviewer(s) can run CI to test the changes comprehensively before merging.

To run CI, PR reviewers can do one of these:

• Add ready label to the PR
• Enable auto-merge.

🚀

[njhill]

@russellb this seems to be failing for some reason on e.g. #9826, any idea why?

Updating PR body
GraphQL: Resource not accessible by integration (updatePullRequest)
Error: Process completed with exit code 1.

[russellb]

@russellb this seems to be failing for some reason on e.g. #9826, any idea why?

Updating PR body
GraphQL: Resource not accessible by integration (updatePullRequest)
Error: Process completed with exit code 1.

hey, apologies, I didn't have a permissions problem when I ran it on my fork, but it's probably because I owned the repo, so the token probably had different permissions by default. I will fix it now.

[russellb]

follow-up here: #10139