Rename fork ReactSharedInternals -> ReactSharedInternalsClient (#27767)

## Summary

Follow up from #27717 based on feedback to rename the fork module itself

## How did you test this change?

- `yarn build`
- `yarn test
packages/scheduler/src/__tests__/SchedulerUMDBundle-test.internal.js`

Co-authored-by: Jack Pope <jackpope@meta.com>

scripts/rollup/forks.js

@@ -225,7 +225,7 @@ const forks = Object.freeze({
       case UMD_DEV:
       case UMD_PROD:
       case UMD_PROFILING:
-        return './packages/react/src/forks/ReactSharedInternals.umd.js';
+        return './packages/react/src/forks/ReactSharedInternalsClient.umd.js';
       default:
         return null;
     }