fix(menu): Add a border on macOS in dark mode and increased contrast

[Saadnajmi]

Platforms Impacted

• [ ] iOS
• [x] macOS
• [ ] win32 (Office)
• [ ] windows
• [ ] android

Description of changes

Add a border to MenuV1 on macOS when increased contrast is enabled. Technically the Menu is now 1 px bigger in Increased contrast is on, but I think that's OK.

Verification

Dark Mode:

Increased Contrast Light:

Increased Contrast Dark:

Pull request checklist

This PR has considered (when applicable):

• [ ] Automated Tests
• [ ] Documentation and examples
• [ ] Keyboard Accessibility
• [ ] Voiceover
• [ ] Internationalization and Right-to-left Layouts