Delete the remainder of groups (#9357)

* Delete the remainder of groups

Fixes https://github.com/vector-im/element-web/issues/22770
Continues https://github.com/matrix-org/matrix-react-sdk/pull/8027

* Don't need the strings either

src/PageTypes.ts

@@ -20,7 +20,6 @@ enum PageType {
     HomePage = "home_page",
     RoomView = "room_view",
     UserView = "user_view",
-    LegacyGroupView = "legacy_group_view",
 }
 
 export default PageType;