This PR should remove all Headstart Annotations from themes in this repo.
Why? Headstart annotations stored in WP.com themes are generated, tested, and sent for translation via WP-CLI scripts running on subversion-ed WordPress sandboxes. I recently updated Headstart annotations for our 20+ recent themes in order to correct some issues in our FSE Plugin and Page Layout feature. When discussing how to get these annotations updated in this themes repo @michaeldcain and came up with two options.
1. Copy-paste back into the affected themes in this repo.
2. Just remove all the Headstart annotations from this repo.
The second option seemed the simplest. It leaves **all** Headstart annotations on WP.com "ignore-able" for this GH repo and reduces the chance of Headstart annotations becoming out of date in this GH repo, potentially reducing future errors.
* Add missing styles for pre tag in classic editor.
* Update button styles, to make sure shine is only applied to buttons without a background, but that the background colour still applies as a fallback.
