Fix the comment command for nightly on a PR

[Dr-Irv]

          @Dr-Irv I understand the error, the initial issue with the comment commands was that it would checkout the main branch and not the one we want to merge so I fixed this. Now the issue is that it is looking for the branch in the pandas-stubs repo although in the current setting the branch in on my personal repo (loicdiridollou/pandas-stubs).

I will fix this in a separate PR, just need to test it on a dummy repo on my end so would be preferable to merge this one (I tested the changes locally running poetry run poe pytest --nightly and it was good.

Originally posted by @loicdiridollou in #1122 (comment)