Merge pull request 'Undo: claiming mesh-broker made lavinmq unbuildable' (#118) from revert/broker-seat-claim into main

Putting the claim back was wrong on its own terms. `mesh-broker` delivers
`mesh-bus`, and a seat that delivers a provision may only be held by a module that
provides it — so the claim is refused at registration:

  lavinmq claims mesh-broker, whose holder answers for "mesh-bus",
  and lavinmq does not provide "mesh-bus" at mesh scope

Which means the merged claim does not restore the holder, it stops lavinmq being
built at all. Removed again.

The seat being empty is still the live fault, and it has only one valid answer: the
holder must provide `mesh-bus`, and the module that does is nats. Recorded against
the rollout, because it moves a step that was optional into the critical path.

modules/lavinmq/module.json

@@ -7,12 +7,6 @@
       "scope": "mesh"
     }
   ],
-  "claims": [
-    {
-      "name": "mesh-broker",
-      "scope": "mesh"
-    }
-  ],
   "capabilities": [
     "container-runtime"
   ],