.github: Update stale messaging add newlines (#51298)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/51298
newlines weren't being respected so just add them through the `<br>` html
tag.
Also changes the wording for open source ones to designate that a
maintainer may be needed to unstale a particular PR.
Signed-off-by: Eli Uriegas <eliuriegas@fb.com>
Test Plan: Imported from OSS
Reviewed By: janeyx99
Differential Revision: D26131126
Pulled By: seemethere
fbshipit-source-id: 465bfc0ba4dc16a7a90e0c03c33d551184e35f5b
