Add dynamic flags to React Native (#21291)

* Add dynamic flags to React Native

* Hardcode the setting to false instead

Author: rickhanlonii

packages/shared/forks/ReactFeatureFlags.native-fb.js

@@ -60,7 +60,7 @@ export const enableUseRefAccessWarning = false;
 export const enableRecursiveCommitTraversal = false;
 export const disableSchedulerTimeoutInWorkLoop = false;
 export const enableLazyContextPropagation = false;
-export const enableSyncDefaultUpdates = true;
+export const enableSyncDefaultUpdates = false;
 
 // Flow magic to verify the exports of this file match the original version.
 // eslint-disable-next-line no-unused-vars