Pass room through the model, not when creating the delegate

This is another thing that enables us to view multiple rooms in a single
timeline. Specifically, this improves the experience in room search
going across room versions and getting a correct readOnly status (for
hiding certain hover actions.)

src/roominfo/RoomMedia.qml

@@ -52,7 +52,6 @@ QQC2.ScrollView {
                 delegate: Timeline.MessageDelegate {
                     alwaysFillWidth: true
                     cardBackground: false
-                    room: root.room
                 }
             }
 
@@ -61,7 +60,6 @@ QQC2.ScrollView {
                 delegate: Timeline.MessageDelegate {
                     alwaysFillWidth: true
                     cardBackground: false
-                    room: root.room
                 }
             }
         }