Docs: Add a `@since` note to `register_rest_route()` about the...

Docs: Add a `@since` note to `register_rest_route()` about the `_doing_it_wrong()` notice when the required `permission_callback` argument is not set.

Follow-up to [48526].

Props psykro.
Merges [48827] to the 5.5 branch.
Fixes #51060.
Built from https://develop.svn.wordpress.org/branches/5.5@48828


git-svn-id: https://core.svn.wordpress.org/branches/5.5@48590 1a063a9b-81f0-0310-95a4-ce76da25c4cd