RN-Tester: Reorder buttons in the New Architecture sample (#48666)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/48666

The New Architecture sample is getting too big and the two views are not visible anymore.
I'm fixing this but having buttons side by side.

Changelog:
[Internal] [Changed] -

Reviewed By: cipolleschi

Differential Revision: D68153245

fbshipit-source-id: 5557fd40f81078fe3994d8efe0e73784e043ed78