[raw_menu_anchor.0.dart] Remove misdrawn emojis. (#162807)

This PR removes the leading emojis displayed on the RawMenuAnchor
example. I knew emojis usually showed up monochrome on web, but code
samples also appear to incorrectly display the emoji source.

Because this change doesn't affect the menu's functionality, I didn't
include additional tests, but I'd be happy to add tests if needed. One
test was modified to account for menu items no longer having a leading
icon.

<img width="1247" alt="image"
src="https://github.com/user-attachments/assets/58a338c8-c882-4ad1-af44-596d91e9f382"
/>

Fixes flutter/flutter#162806

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we expect every widget to implement].
- [x] I signed the [CLA].
- [x] I listed at least one issue that this PR fixes in the description
above.
- [x] I updated/added relevant documentation (doc comments with `///`).
- [ ] I added new tests to check the change I am making, or this PR is
[test-exempt].
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Fixes] where supported.
- [x] All existing and new tests are passing.

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---------

Co-authored-by: Tirth <pateltirth454@gmail.com>

Author: davidhicks980

examples/api/lib/widgets/raw_menu_anchor/raw_menu_anchor.0.dart

@@ -12,14 +12,13 @@ void main() {
 }
 
 enum Animal {
-  cat('Cat', leading: Text('🦁')),
-  kitten('Kitten', leading: Text('🐱')),
-  felisCatus('Felis catus', leading: Text('🐈')),
-  dog('Dog', leading: Text('🐕'));
+  cat('Cat'),
+  kitten('Kitten'),
+  felisCatus('Felis catus'),
+  dog('Dog');
 
-  const Animal(this.label, {this.leading});
+  const Animal(this.label);
   final String label;
-  final Widget? leading;
 }
 
 class RawMenuAnchorExample extends StatefulWidget {
@@ -81,7 +80,6 @@ class _RawMenuAnchorExampleState extends State<RawMenuAnchorExample> {
                     });
                     controller.close();
                   },
-                  leadingIcon: SizedBox(width: 24, child: Center(child: animal.leading)),
                   trailingIcon:
                       _selectedAnimal == animal ? const Icon(Icons.check, size: 20) : null,
                   child: Text(animal.label),

examples/api/test/widgets/raw_menu_anchor/raw_menu_anchor.0_test.dart

@@ -27,7 +27,7 @@ void main() {
     expect(find.text(dogLabel), findsOneWidget);
     expect(
       tester.getRect(find.ancestor(of: find.text(catLabel), matching: find.byType(TapRegion))),
-      rectMoreOrLessEquals(const Rect.fromLTRB(447.2, 328.0, 662.3, 532.0), epsilon: 0.1),
+      rectMoreOrLessEquals(const Rect.fromLTRB(447.2, 328.0, 626.3, 532.0), epsilon: 0.1),
     );
 
     // Close the menu.
@@ -90,7 +90,7 @@ void main() {
 
     expect(
       tester.getRect(find.ancestor(of: find.text(catLabel), matching: find.byType(TapRegion))),
-      rectMoreOrLessEquals(const Rect.fromLTRB(447.2, 328.0, 662.3, 532.0), epsilon: 0.1),
+      rectMoreOrLessEquals(const Rect.fromLTRB(447.2, 328.0, 626.3, 532.0), epsilon: 0.1),
     );
 
     expect(