Change returning value of DirectEventHandler and BubblingEventHandler to void

Summary:
returning type of Bubbling and Direct Event should be always void of Promise (if async). Other situations shouldn't be permitted.
Reformated all cases when it the function wasn't void.

Reviewed By: rickhanlonii

Differential Revision: D16165962

fbshipit-source-id: 7c1377c3ed4bd54a431a13e5bcda4f7ec0adf4dc

Libraries/Components/RefreshControl/RefreshControl.js

@@ -81,7 +81,7 @@ export type RefreshControlProps = $ReadOnly<{|
   /**
    * Called when the view starts refreshing.
    */
-  onRefresh?: ?() => mixed,
+  onRefresh?: ?() => void,
 
   /**
    * Whether the view should be indicating an active refresh.