fix: improve the grammar/clarity of the stale bot comments (#52124)

Summary:
this PR makes the stale bot messages a bit clearer and fixes a grammatical issue.

# Changelog:

[INTERNAL] [FIXED] Tweak stale bot messages

Pull Request resolved: https://github.com/facebook/react-native/pull/52124

Test Plan: N/A

Reviewed By: andrewdacenko

Differential Revision: D76969503

Pulled By: cortinico

fbshipit-source-id: d030a0488b44521f61447e252bae5ded10826dbb