Use 'constKeyword' as entity name in ConstantPattern.

Change-Id: Ib2286c9a13cf758f0b6040478d93dca23c6b3013
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/427940
Reviewed-by: Paul Berry <[email protected]>
Commit-Queue: Konstantin Shcheglov <[email protected]>

Author: scheglov

pkg/analyzer/lib/src/dart/ast/ast.dart

@@ -4259,7 +4259,7 @@ final class ConstantPatternImpl extends DartPatternImpl
   @override
   ChildEntities get _childEntities =>
       super._childEntities
-        ..addToken('const', constKeyword)
+        ..addToken('constKeyword', constKeyword)
         ..addNode('expression', expression);
 
   @override