Slider fromUser is required

Summary: This was a mismatch with the schema

Reviewed By: cpojer

Differential Revision: D15960977

fbshipit-source-id: 08a56ac404eb5d45c6363e4574bd3d7bacf3ca08

Author: rickhanlonii

Libraries/Components/Slider/SliderNativeComponent.js

@@ -25,7 +25,7 @@ import type {ViewProps} from '../View/ViewPropTypes';
 
 type Event = $ReadOnly<{|
   value: Float,
-  fromUser?: boolean,
+  fromUser: boolean,
 |}>;
 
 type NativeProps = $ReadOnly<{|