update resolution-aware asset docs links (#128769)

Updates some doc comment links.

Fixes #128139

packages/flutter/lib/src/services/asset_manifest.dart

@@ -15,7 +15,7 @@ import 'message_codecs.dart';
 const String _kAssetManifestFilename = 'AssetManifest.bin';
 
 /// Contains details about available assets and their variants.
-/// See [Asset variants](https://docs.flutter.dev/development/ui/assets-and-images#asset-variants)
+/// See [Resolution-aware image assets](https://docs.flutter.dev/ui/assets-and-images#resolution-aware)
 /// to learn about asset variants and how to declare them.
 abstract class AssetManifest {
   /// Loads asset manifest data from an [AssetBundle] object and creates an
@@ -31,8 +31,8 @@ abstract class AssetManifest {
   /// file at build time.
   ///
   /// See [Specifying assets](https://docs.flutter.dev/development/ui/assets-and-images#specifying-assets)
-  /// and [Loading assets](https://docs.flutter.dev/development/ui/assets-and-images#loading-assets) for more
-  /// information.
+  /// and [Loading assets](https://docs.flutter.dev/development/ui/assets-and-images#loading-assets)
+  /// for more information.
   List<String> listAssets();
 
   /// Retrieves metadata about an asset and its variants. Returns null if the
@@ -119,7 +119,7 @@ class AssetMetadata {
   /// This will be null if the parent folder name is not a ratio value followed
   /// by an "x".
   ///
-  /// See [Declaring resolution-aware image assets](https://docs.flutter.dev/development/ui/assets-and-images#resolution-aware)
+  /// See [Resolution-aware image assets](https://docs.flutter.dev/development/ui/assets-and-images#resolution-aware)
   /// for more information.
   final double? targetDevicePixelRatio;
 
@@ -129,8 +129,5 @@ class AssetMetadata {
 
   /// Whether or not this is a main asset. In other words, this is true if
   /// this asset is not a variant of another asset.
-  ///
-  /// See [Asset variants](https://docs.flutter.dev/development/ui/assets-and-images#asset-variants)
-  /// for more about asset variants.
   final bool main;
 }