[hooks] Remove explicit adding of source dependency in hook/link.dart scripts (#1632)

Author: mkustermann

pkgs/native_assets_builder/test_data/drop_dylib_link/hook/link.dart

@@ -14,6 +14,5 @@ Received ${config.codeAssets.all.length} encodedAssets: ${config.codeAssets.all.
     print('''
 Keeping only ${output.codeAssets.all.map((e) => e.id)}.
 ''');
-    output.addDependency(config.packageRoot.resolve('hook/link.dart'));
   });
 }

pkgs/native_assets_builder/test_data/no_asset_for_link/hook/link.dart

@@ -7,6 +7,5 @@ import 'package:native_assets_cli/native_assets_cli.dart';
 void main(List<String> arguments) async {
   await link(arguments, (config, output) async {
     output.addEncodedAssets(config.encodedAssets);
-    output.addDependency(config.packageRoot.resolve('hook/link.dart'));
   });
 }