- Removes `requires_approve?`. This was only being used
   in `merge_request_presenter` to hide/show the API paths.
- Adds `approval_feature_available?`
   The API path checks have been updated to use this call.
- Replaces `approvalsRequired` in the mr_widget_store with
   `hasApprovalsAvailable`. The previous property actually
   only checked if the `approvalsPath` was truthy or not. It
   looked like it checked the `approvalsRequired` from the
   server, but since this was camel case, this value never existed.