Remove unnecessary feature flags from fantom tests (#52101)

Summary:
Pull Request resolved: #52101

Changelog: [internal]

`enableAccessToHostTreeInFabric` is enabled by default in tests, so doesn't need to be explicitly set.

Reviewed By: lenaic

Differential Revision: D76894319

fbshipit-source-id: 437a763bd9c557ecbafa53e31410da1120151b86

Author: rubennorte

packages/react-native/src/private/renderer/consistency/__tests__/UIConsistency-itest.js

@@ -4,7 +4,6 @@
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  *
- * @fantom_flags enableAccessToHostTreeInFabric:true
  * @fantom_flags enableSynchronousStateUpdates:true
  * @flow strict-local
  * @format

packages/react-native/src/private/webapis/intersectionobserver/__tests__/IntersectionObserver-benchmark-itest.js

@@ -4,7 +4,7 @@
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  *
- * @fantom_flags enableAccessToHostTreeInFabric:true enableIntersectionObserverEventLoopIntegration:*
+ * @fantom_flags enableIntersectionObserverEventLoopIntegration:*
  * @flow strict-local
  * @format
  */