Update messages for @react-native-bot (#47428)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/47428

This changes the messages that the bot is printing.
I've moved from using a table to using GitHub's admonitions that
renders nicely are are more informative.

Changelog:
[Internal] [Changed] - Update messages for react-native-bot

Reviewed By: mdvacca

Differential Revision: D65485633

fbshipit-source-id: f43f7bd75280bfd0aceab48b2517306c1057b778