Remove redundant feature flag in the test due to facebook#12117

Author: NE-SmallTown

packages/react-dom/src/events/__tests__/ChangeEventPlugin-test.internal.js

@@ -475,7 +475,6 @@ describe('ChangeEventPlugin', () => {
     beforeEach(() => {
       jest.resetModules();
       ReactFeatureFlags = require('shared/ReactFeatureFlags');
-      ReactFeatureFlags.enableAsyncSubtreeAPI = true;
       ReactFeatureFlags.debugRenderPhaseSideEffectsForStrictMode = false;
       ReactFeatureFlags.debugRenderPhaseSideEffectsForStrictMode = false;
       ReactDOM = require('react-dom');

packages/react-dom/src/events/__tests__/SimpleEventPlugin-test.internal.js

@@ -246,7 +246,6 @@ describe('SimpleEventPlugin', function() {
     beforeEach(() => {
       jest.resetModules();
       ReactFeatureFlags = require('shared/ReactFeatureFlags');
-      ReactFeatureFlags.enableAsyncSubtreeAPI = true;
       ReactFeatureFlags.debugRenderPhaseSideEffectsForStrictMode = false;
       ReactDOM = require('react-dom');
     });