Set explicitely parent in MaximizeComponent

Currently it uses applicationWindow().overlay which works but is
not ideal for multiple reasons:

- This as a tendency to breaks unexpectedly
- It can't be optimized by the qml compiler

So we are trying to move away from these construct everywhere.

src/qml/RoomPage.qml

@@ -309,6 +309,7 @@ Kirigami.Page {
         NeochatMaximizeComponent {
             currentRoom: root.currentRoom
             model: root.mediaMessageFilterModel
+            parent: root.QQC2.Overlay.overlay
         }
     }
 }