Fixeds a typo in VibrationExample.js

Summary:
Just found this typo in `Examples/UIExplorer/js/VibrationExample.js` and fixed it.
Closes https://github.com/facebook/react-native/pull/13593

Differential Revision: D4921094

Pulled By: javache

fbshipit-source-id: f0945ee0786061f98c634a3f1408c7358d930304

Examples/UIExplorer/js/VibrationExample.js

@@ -55,7 +55,7 @@ vibration length on iOS is fixed.
 pattern controls durations BETWEEN each vibration only.
 
 arg 0: duration to wait before turning the vibrator on.
-subsequent args: duration to wait before next vibrattion.
+subsequent args: duration to wait before next vibration.
 `;
 }