RN: Cleanup ReactNativeInternalFeatureFlagsMock (#44445)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/44445

The `ReactNativeInternalFeatureFlagsMock` module is not references in the open source repository, so there's no reason it should exist there. This cleans that up.

Changelog:
[Internal]

Reviewed By: kassens

Differential Revision: D57052284

fbshipit-source-id: d220eae2ba76f20ed48742779fbffd5de1f77529

jest.config.js

@@ -41,12 +41,6 @@ module.exports = {
     defaultPlatform: 'ios',
     platforms: ['ios', 'android'],
   },
-  moduleNameMapper: {
-    // This module is internal to Meta and used by their custom React renderer.
-    // In tests, we can just use a mock.
-    '^ReactNativeInternalFeatureFlags$':
-      '<rootDir>/packages/react-native/jest/ReactNativeInternalFeatureFlagsMock.js',
-  },
   moduleFileExtensions: ['fb.js'].concat(defaults.moduleFileExtensions),
   modulePathIgnorePatterns: ['scripts/.*/__fixtures__/'],
   unmockedModulePathPatterns: [

packages/react-native/jest/ReactNativeInternalFeatureFlagsMock.js

@@ -1,13 +0,0 @@
-/**
- * Copyright (c) Meta Platforms, Inc. and affiliates.
- *
- * This source code is licensed under the MIT license found in the
- * LICENSE file in the root directory of this source tree.
- *
- * @format
- * @flow strict
- */
-
-'use strict';
-
-module.exports = {};