It's the metal clip left of the bracket, you can see the other end of the clip, straight up, with a dimple on it. Might have to compress the black plastic tabs to pull it through, can't remember for sure. I usually use a 1/4" drive socket, extension and a ratchet to get the bolts out, and don't bother removing the cable from the bracket.
You have to know how it works,
to figure out why it doesn't.