Fix super method call in private instance method calling overridden method (#9801)

* Fix super method call in private instance method calling overridden method

* Change return value in test fixtures

* Update tests to verify that overridden method is not called

packages/babel-helper-create-class-features-plugin/src/fields.js

@@ -501,7 +501,9 @@ function replaceThisContext(path, ref, superRef, file, loose) {
     file,
     getObjectRef() {
       state.needsClassRef = true;
-      return path.node.static ? ref : t.thisExpression();
+      return path.node.static
+        ? ref
+        : t.memberExpression(ref, t.identifier("prototype"));
     },
   });
   replacer.replace();