Remove warning against PR for release branch
Remove warning against PR for release branch

Summary:
Changelog: [Internal] Remove warning about creating a pull request to a release branch

We want to support this use case as we want pick requesters to land the cherry-picks themselves and rely on CircleCI automation to test

Reviewed By: cortinico

Differential Revision: D32780819

fbshipit-source-id: 882625a016653dbf480da33fd499d3718b2b5524

facebook/react-native,javache/react-native,facebook/react-native,janicduplessis/react-native,javache/react-native,facebook/react-native,janicduplessis/react-native,janicduplessis/react-native,facebook/react-native,facebook/react-native,facebook/react-native,facebook/react-native,janicduplessis/react-native,facebook/react-native,javache/react-native,janicduplessis/react-native,javache/react-native,facebook/react-native,javache/react-native,janicduplessis/react-native,javache/react-native,javache/react-native,janicduplessis/react-native,janicduplessis/react-native,javache/react-native,javache/react-native