qapi: Stop rejecting #optional Commit 1d8bda1 got rid of #optional tags, and added a check to keep them from getting added back, to make sure patches then in flight don't add them back. It's been six months, time to drop that check. Signed-off-by: Markus Armbruster <armbru@redhat.com> Message-Id: <20171002141341.24616-3-armbru@redhat.com> Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>