chore: remove deprecated "X-UA-Compatible" and "apple-mobile-web-app-capable" metas

[mcdurdin]

For Keyman Developer Server, add app.webmanifest so that it can be saved to the home screen; other pages should not require this.

Fixes: #16172
Test-bot: skip

[keymanapp-test-bot]

User Test Results

Test specification and instructions

User tests are not required

Test Artifacts

• Android
  • Keyman for Android apk - build : all tests passed (no artifacts on BuildLevel "build")
  • FirstVoices Keyboards for Android apk - build : all tests passed (no artifacts on BuildLevel "build")
  • FirstVoices Keyboards for Android apk (old PRs) - build : all tests passed (no artifacts on BuildLevel "build")
  • KeyboardHarness apk - build : all tests passed (no artifacts on BuildLevel "build")
  • Keyman for Android apk (old PRs) - build : all tests passed (no artifacts on BuildLevel "build")
  • KMSample1 apk - build : all tests passed (no artifacts on BuildLevel "build")
  • KMSample2 apk - build : all tests passed (no artifacts on BuildLevel "build")
• Developer
  • Keyman Developer - build : all tests passed (no artifacts on BuildLevel "build")
  • Compiler Regression Tests - build : all tests passed (no artifacts on BuildLevel "build")
  • Keyman Developer (old PRs) - build : all tests passed (no artifacts on BuildLevel "build")
  • kmcomp.zip - build : all tests passed (no artifacts on BuildLevel "build")
  • kmcomp.zip (old PRs) - build : all tests passed (no artifacts on BuildLevel "build")
• iOS
  • Keyman for iOS (simulator image) - build : all tests passed (no artifacts on BuildLevel "build")
  • FirstVoices Keyboards for iOS (simulator image) - build : all tests passed (no artifacts on BuildLevel "build")
  • FirstVoices Keyboards for iOS (simulator image) (old PRs) - build : all tests passed (no artifacts on BuildLevel "build")
  • Keyman for iOS (simulator image) (old PRs) - build : all tests passed (no artifacts on BuildLevel "build")
• Keyboards
  • Test Keyboards - build : all tests passed (no artifacts on BuildLevel "build")
• Web
  • KeymanWeb Test Home - build : all tests passed (no artifacts on BuildLevel "build")
• Windows
  • Keyman for Windows - build : all tests passed (no artifacts on BuildLevel "build")
  • FirstVoices Keyboards for Windows - build : all tests passed (no artifacts on BuildLevel "build")
  • FirstVoices Keyboards for Windows (old PRs) - build : all tests passed (no artifacts on BuildLevel "build")
  • Keyman for Windows (old PRs) - build : all tests passed (no artifacts on BuildLevel "build")
  • Text Editor (ARM64) - build : all tests passed (no artifacts on BuildLevel "build")
  • Text Editor (x64) - build : all tests passed (no artifacts on BuildLevel "build")
  • Text Editor (x86) - build : all tests passed (no artifacts on BuildLevel "build")