Summary:
We've been getting a lot of documentation PRs opened against `0.29-stable`, `0.30-stable`, and so on, instead of `master`. This is because our doc site is also based on RN release cuts, so clicking on the "Edit on GitHub" links on a document will take you to the markdown source for that release branch instead of the latest doc on `master`.

See #9095 for an example of such a PR.

In this PR we edit the link to say View on GitHub. Though it may not prevent PRs from being opened against a release branch, removing the "Edit" CTA may help in this regard.
Closes https://github.com/facebook/react-native/pull/9149

Differential Revision: D3664368

Pulled By: vjeux

fbshipit-source-id: 395c0813f736bfbe1be4b4fb1182f9060169365d