Return 404 instead of 403 for summaries of missing rooms

src/api/client/room/summary.rs

@@ -39,7 +39,7 @@ pub(crate) async fn get_room_summary(
 			Err!(Request(Forbidden("You may not preview this room."), FORBIDDEN))
 		},
 		| Accessibility::NotFound => {
-			Err!(Request(Forbidden("This room does not exist."), FORBIDDEN))
+			Err!(Request(NotFound("This room does not exist."), FORBIDDEN))
 		},
 	}
 }