Tweak github CI

[pali]

The point to run git diff was at the time when git repo has lot of autogenerated files, it was added during review to detect that all files are re-generated and up-to-date and once all autogenerated files were removed from the git repository, also running git diff was removed from the CI, as it was useless then.

I'm not sure why running git diff was reintroduced again into CI, but changing it to git diff --quiet ||: is absolutely useless as it ignores return value when repo is modified and so, the command never fails. So this command now does absolutely nothing.

[atoomic]

I was trying to preserve the best of both worlds... git diff being still there and displayed as hint if needed but not blocking I'm not sure what reintroduced it, but I m also fine removing it

[pali]

I guess it was some of rebase issue (maybe older pull request was based on old commit and then merge conflicts were resolved incorrectly, and unintentionally was it reintroduced - I saw these mistakes lot of times). So just remove git diff, it has no point here.

[atoomic]

FYI I just removed the git diff from the workflow