lightbox test: Skip a no-hero test, pending rework for new page transitions

This test relies on background assumptions about how the "back" page
transition work which are true of the current default transitions on
Android (the default target platform of tests), but are broken by the
upcoming introduction of predictive back:
  flutter/flutter#165832 (comment)

For a quick unblocking of the upstream change, skip the test.

In principle there's no reason a test like this can't work with the
upcoming upstream behavior; it'll just need to work a little
differently.  But leave that for a follow-up change.

Author: gnprice

test/widgets/lightbox_test.dart

@@ -275,6 +275,7 @@ void main() {
     });
 
     testWidgets('no hero animation occurs between different message list pages for same image', (tester) async {
+      // Regression test for: https://github.com/zulip/zulip-flutter/issues/930
       Rect getElementRect(Element element) =>
         tester.getRect(find.byElementPredicate((e) => e == element));
 
@@ -310,7 +311,13 @@ void main() {
       }
 
       debugNetworkImageHttpClientProvider = null;
-    });
+    }, skip: true, // TODO get this no-hero test to work again with new page transitions;
+      //   see https://github.com/flutter/flutter/pull/165832#issuecomment-3111641360 .
+      //   Perhaps specify the old default, of ZoomPageTransitionsBuilder?
+      //   Or make getElementRect work relative to the enclosing page,
+      //   rather than the whole screen, so that the test becomes robust to
+      //   the whole pages moving around.
+    );
   });
 
   group('_ImageLightboxPage', () {