Use pullbot token instead of GITHUB_TOKEN on the Danger Action (#33900)

Summary:
GITHUB_TOKEN doesn't have write permissions on forks, using the pullbot token instead.

https://docs.github.com/en/actions/security-guides/automatic-token-authentication#permissions-for-the-github_token

## Changelog

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[Internal] - Use pullbot token instead of GITHUB_TOKEN on the Danger Action

Pull Request resolved: https://github.com/facebook/react-native/pull/33900

Test Plan: CI will validate it

Reviewed By: cipolleschi

Differential Revision: D36627043

Pulled By: f-meloni

fbshipit-source-id: bc7ff2f463c9d7cac61d362440858945edfbdbaf