Summary:
Update ccache key to use github.ref

## Changelog:

[INTERNAL] - Update ccache key to use github.ref

Pull Request resolved: https://github.com/facebook/react-native/pull/45698

Test Plan: CI

Reviewed By: blakef

Differential Revision: D60277122

Pulled By: cortinico

fbshipit-source-id: 10437e56a398e817fb030d505fbdb6cf7c23031a