Reduce some log spam from MatrixRTCSession.callMembershipsForRoom (#3812)

This gets logged very frequently - including once for each room at startup -
and it's filling the logs.

src/matrixrtc/MatrixRTCSession.ts

@@ -118,10 +118,12 @@ export class MatrixRTCSession extends TypedEventEmitter<MatrixRTCSessionEvent, M
         }
 
         callMemberships.sort((a, b) => a.createdTs() - b.createdTs());
+        if (callMemberships.length > 1) {
             logger.debug(
-            "Call memberships, in order: ",
+                `Call memberships in room ${room.roomId}, in order: `,
                 callMemberships.map((m) => [m.createdTs(), m.sender]),
             );
+        }
 
         return callMemberships;
     }