[analyzer] Remove unused method _includeNameOffsetInIdentifier.

This is a step towards enabling the `comment_references` lint in the
analyzer codebase.

Change-Id: I6a6a69641e9926c110b8cf43bd3cb3a3ce393dc8
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/450721
Auto-Submit: Paul Berry <[email protected]>
Commit-Queue: Konstantin Shcheglov <[email protected]>
Reviewed-by: Konstantin Shcheglov <[email protected]>

Author: stereotype441

pkg/analyzer/lib/src/dart/element/element.dart

@@ -3695,12 +3695,6 @@ abstract class FragmentImpl with _FragmentImplMixin implements Fragment {
     return asElement2?.sinceSdkVersion;
   }
 
-  /// Whether to include the [nameOffset] in [identifier] to disambiguate
-  /// elements that might otherwise have the same identifier.
-  bool get _includeNameOffsetInIdentifier {
-    return false;
-  }
-
   @override
   bool operator ==(Object other) {
     return identical(this, other);
@@ -7592,13 +7586,6 @@ class LocalFunctionFragmentImpl extends FunctionFragmentImpl
     required super.name,
     required super.firstTokenOffset,
   });
-
-  @override
-  bool get _includeNameOffsetInIdentifier {
-    return super._includeNameOffsetInIdentifier ||
-        enclosingFragment is ExecutableFragment ||
-        enclosingFragment is VariableFragment;
-  }
 }
 
 class LocalVariableElementImpl extends PromotableElementImpl