.github: Make on_pull_request a conditional block (#58363)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/58363
Previous implemntation relied on us directly writing the yaml instead of
just having a conditional block, this allows us better readability for
pull request triggers
Signed-off-by: Eli Uriegas <seemethere101@gmail.com>
Test Plan: Imported from OSS
Reviewed By: walterddr
Differential Revision: D28465271
Pulled By: seemethere
fbshipit-source-id: fd556bb6bac4954fcddb4a2b0383e996f292a794
