Fix Vibration.vibrate() allowing null params

Summary:
The flow type allows these parameters to be optional but not null. Make TS the same.

Changelog:
[General][Fixed] - Fix Vibration.vibrate() allowing null params

Reviewed By: christophpurrer

Differential Revision: D42046301

fbshipit-source-id: a030d4f141a526dfe2f0fb3a90e36e641fa6d789

Libraries/Vibration/Vibration.d.ts

@@ -31,7 +31,7 @@
  * V(fixed) --wait(1s)--> V(fixed) --wait(2s)--> V(fixed) --wait(3s)--> V(fixed)
  */
 export interface VibrationStatic {
-  vibrate(pattern?: number | number[] | null, repeat?: boolean | null): void;
+  vibrate(pattern?: number | number[], repeat?: boolean): void;
 
   /**
    * Stop vibration