Move layout plugin sidebar extensions to the plugin package

Summary: Moved layout plugin sidebar extensions to the plugin package.

Reviewed By: passy

Differential Revision: D27036489

fbshipit-source-id: 5b3406e5c50ba61709d925a3c0cb07a6fd7552db

desktop/scripts/get-app-watch-folders.ts

@@ -19,7 +19,6 @@ import isFB from './isFB';
  */
 const pluginsReferencedDirectlyFromFlipper = [
   path.join(publicPluginsDir, 'navigation'),
-  path.join(fbPluginsDir, 'layout', 'sidebar_extensions'),
   path.join(fbPluginsDir, 'mobileconfig'),
   path.join(fbPluginsDir, 'watch'),
 ];