MDL-78129 communication_matrix: Stop marking users as synced

No need to sync users for role changes.

Power level changes do not need to happen after being added to a room.
They can happen in any order and persist after a user is removed.

communication/provider/matrix/classes/communication_feature.php

@@ -192,8 +192,6 @@ class communication_feature implements
 
     public function update_room_membership(array $userids): void {
         $this->set_matrix_power_levels();
-        // Mark then users as synced for the updated members.
-        $this->processor->mark_users_as_synced($userids);
     }
 
     /**