Remove irrelevant function

test/components/views/rooms/RoomList-test.js

@@ -56,11 +56,6 @@ describe('RoomList', () => {
 
         DMRoomMap.makeShared();
 
-        // Lie to the room list store about DMs not existing
-        DMRoomMap.getUserIdForRoomId = () => {
-            return null;
-        };
-
         parentDiv = document.createElement('div');
         document.body.appendChild(parentDiv);