Move "Automatic platform adaptations" page to Adaptive design section…

… in Left Nav (#11473)

_Issues fixed by this PR :_ #11442 
This PR moves the `Automatic platform adaptations` page to section
`Adaptive & responsive design` in nav bar and closes the above issue.

## Presubmit checklist

- [X] This PR doesn’t contain automatically generated corrections
(Grammarly or similar).
- [X] This PR follows the [Google Developer Documentation Style
Guidelines](https://developers.google.com/style) — for example, it
doesn’t use _i.e._ or _e.g._, and it avoids _I_ and _we_ (first person).
- [X] This PR uses [semantic line
breaks](https://github.com/dart-lang/site-shared/blob/main/doc/writing-for-dart-and-flutter-websites.md#semantic-line-breaks)
of 80 characters or fewer.

---------

Co-authored-by: Shams Zakhour (ignore Sfshaza) <[email protected]>

firebase.json

@@ -138,6 +138,7 @@
       { "source": "/platform-integration/c-interop", "destination": "/platform-integration", "type": 301 },
       { "source": "/platform-integration/ios-app-clip", "destination": "/platform-integration/ios/ios-app-clip", "type": 301 },
       { "source": "/platform-integration/ios/splash-screen", "destination": "/platform-integration/ios/launch-screen", "type": 301 },
+      { "source": "/platform-integration/platform-adaptations", "destination": "/ui/adaptive-responsive/platform-adaptations", "type": 301 },
       { "source": "/platform-integration/platform-views", "destination": "/platform-integration/android/platform-views", "type": 301 },
       { "source": "/platform-integration/web-images", "destination": "/platform-integration/web/web-images", "type": 301 },
       { "source": "/platform-integration/web/initialization-legacy", "destination": "/platform-integration/web/initialization", "type": 301 },

src/_data/sidenav.yml

@@ -211,6 +211,8 @@
       permalink: /ui/adaptive-responsive/input
     - title: Capabilities & policies
       permalink: /ui/adaptive-responsive/capabilities
+    - title: Automatic platform adaptations
+      permalink: /ui/adaptive-responsive/platform-adaptations
     - title: Best practices
       permalink: /ui/adaptive-responsive/best-practices
     - title: Additional resources
@@ -454,8 +456,6 @@
       permalink: /platform-integration/desktop
     - title: Write platform-specific code
       permalink: /platform-integration/platform-channels
-    - title: Automatic platform adaptations
-      permalink: /platform-integration/platform-adaptations
     - title: Android
       permalink: /platform-integration/android
       children: