msglist test: Remove redundant copy of a regression test.

A test on CombinedFeedNarrow is sufficient for preventing this
particular regression. We could go further and test this on other
narrows, but there's little to gain because the bug related to the
absence of a compose box, not any other detail of the narrow.

Signed-off-by: Zixuan James Li <[email protected]>

Author: PIG208

test/widgets/message_list_test.dart

@@ -135,19 +135,6 @@ void main() {
       final padding = MediaQuery.of(element).padding;
       check(padding).equals(EdgeInsets.zero);
     });
-
-    testWidgets('content in MentionsNarrow not asked to consume insets (including bottom)', (tester) async {
-      const fakePadding = FakeViewPadding(left: 10, top: 10, right: 10, bottom: 10);
-      tester.view.viewInsets = fakePadding;
-      tester.view.padding = fakePadding;
-
-      await setupMessageListPage(tester, narrow: const MentionsNarrow(),
-        messages: [eg.streamMessage(content: ContentExample.codeBlockPlain.html, flags: [MessageFlag.mentioned])]);
-
-      final element = tester.element(find.byType(CodeBlock));
-      final padding = MediaQuery.of(element).padding;
-      check(padding).equals(EdgeInsets.zero);
-    });
   });
 
   testWidgets('smoke test for light/dark/lerped', (tester) async {