fetch: Recognize hiddentext as non-retryable
An update to the cirrus api will soon emit this instead of blowing up when requesting a revision that has been hidden. We treat this as a non-retryable error and fail the request.
This is only checked in the revision endpoint, the rerender endpoint should never see these as it request by page id and the most recent revision cannot be hidden. If it did somehow arrive there it would result in an InvalidMWApiResponseException and be retried a few times, probably for the best as a newer revision must be available.
Change-Id: I96ec35f06a4cfc399e019407a8db48ec164455b0