msglist test: Remove redundant regression test.

A test on CombinedFeedNarrow is sufficient for preventing this particular
regression.  We could go further and test this on other narrows that do
not have a compose box (at the time CombinedFeedNarrow was the only narrow
without it), but there is little to gain other than verifying that the
same fix applies to those narrows as well, assuming that we also add a
check to confirm that the compose box is absent.

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 {