[MNT] Remove outdated add_pr2project.yml workflow

[alyssadai]

• Part of Remove outdated add_pr2project.yml from repos workflows#119

• This wf is currently failing on all PRs due to outdated credentials

Checklist

This section is for the PR reviewer

• PR has an interpretable title with a prefix ([ENH], [FIX], [REF], [TST], [CI], [MNT], [INF], [MODEL], [DOC]) (see our Contributing Guidelines for more info)
• PR links to GitHub issue with mention Closes #XXXX
• Tests pass
• Checks pass

For new features:

• Tests have been added

For bug fixes:

• There is at least one test that would fail under the original bug conditions.