Fix hint unused_shown_name

Change-Id: Iefad837b2ef5271b8698872c3fcdd01b936bd6c8
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/100860
Auto-Submit: Paul Berry <paulberry@google.com>
Commit-Queue: Konstantin Shcheglov <scheglov@google.com>
Reviewed-by: Konstantin Shcheglov <scheglov@google.com>

pkg/analyzer/lib/src/summary2/link.dart

@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 import 'package:analyzer/dart/analysis/session.dart';
-import 'package:analyzer/dart/ast/ast.dart' show AstNode, CompilationUnit;
+import 'package:analyzer/dart/ast/ast.dart' show CompilationUnit;
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/src/dart/element/element.dart';
 import 'package:analyzer/src/dart/element/inheritance_manager2.dart';