Enable moveBefore in experimental

Author: sebmarkbage

packages/shared/ReactFeatureFlags.js

@@ -193,7 +193,7 @@ export const disableLegacyContext = true;
 export const disableLegacyContextForFunctionComponents = true;
 
 // Enable the moveBefore() alternative to insertBefore(). This preserves states of moves.
-export const enableMoveBefore = false;
+export const enableMoveBefore = __EXPERIMENTAL__;
 
 // Disabled caching behavior of `react/cache` in client runtimes.
 export const disableClientCache = true;