Remove dynamicColor from remaining demo controllers

[joannaquu]

Platforms Impacted

• iOS
• macOS

Description of changes

Cleaning up some remaining instances of dynamicColor in our demo controllers. Followup to #1655.

Binary change

Total increase: 0 bytes
Total decrease: 0 bytes

File	Before	After	Delta
Total	46,418,544 bytes	46,418,544 bytes	🎉 0 bytes

Full breakdown

File	Before	After	Delta

Verification

Visual Verification

Before	After

Pull request checklist

This PR has considered:

• Light and Dark appearances
• iOS supported versions (all major versions greater than or equal current target deployment version)
• VoiceOver and Keyboard Accessibility
• Internationalization and Right to Left layouts
• Different resolutions (1x, 2x, 3x)
• Size classes and window sizes (iPhone vs iPad, notched devices, multitasking, different window sizes, etc)
• iPad Pointer interaction
• SwiftUI consumption (validation or new demo scenarios needed)
• Objective-C exposure (provide it only if needed)

Microsoft Reviewers: codeflow:open?pullrequest=#1832