Remove outdated add_pr2project.yml from repos

[alyssadai]

This is an old workflow that used to be synced as part of the sync workflow, but was removed in #35. In that PR we added a config option to "delete orphaned files", but it looks like since we refactored the synced file directories at some point since then, this old workflow didn't get deleted cleanly.

The following repos still have this workflow and need it to be deleted:

• neurobagel/documentation
• neurobagel/digest
• neurobagel/project (archived, so less of a problem)

When it runs, it's currently failing due to bad credentials (b/c it's using our deprecated NB_PROJECT_PAT).

[surchs]

Thanks @alyssadai for dealing with this. As I mentioned in https://github.com/neurobagel/project/pull/175, it seems that the bot which replaces the old workflow doesn't work on private repos. We only have the one private repo and we don't really use it much if at all. But it would still be nice to see if we can make the bot work on private repos as well so we have a full solution. Any ideas?

[alyssadai]

The mystery was resolved 😎: https://github.com/neurobagel/project/pull/175#issuecomment-2529289205