Turn off enableSyncDefaultUpdates in test renderer (#21319)

Author: rickhanlonii

packages/shared/forks/ReactFeatureFlags.test-renderer.www.js

@@ -59,7 +59,7 @@ 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