Use the forget function to leave a room everywhere

Use the forget function to leave a room everywhere this is both for consistency and to reduce dependencies. This way no dependency on RoomManager is required to leave a room and since in all cases they have an object they can just call the function.

src/app/qml/RoomPage.qml

@@ -139,8 +139,6 @@ Kirigami.Page {
         anchors.fill: parent
         sourceComponent: SpaceHomePage {
             room: root.currentRoom
-
-            onRequestLeaveRoom: room => RoomManager.leaveRoom(room);
         }
     }