Use Context.getSystemService(Class<T>) for InputManager.

This is a mechanical replacement of Context.getSystemService(String)
with Context.getSystemService(Class<T>) when retrieving InputManager.
Note those are bundled code.  Hence we don't need to make sure
Build.VERSION.SDK_INT >= 23.

Change-Id: Iee47e374e1349720e3100bab33ed139e1f47c169
diff --git a/services/core/java/com/android/server/VibratorService.java b/services/core/java/com/android/server/VibratorService.java
index 9eb66dd..2924cef 100644
--- a/services/core/java/com/android/server/VibratorService.java
+++ b/services/core/java/com/android/server/VibratorService.java
@@ -223,7 +223,7 @@
     }
 
     public void systemReady() {
-        mIm = (InputManager)mContext.getSystemService(Context.INPUT_SERVICE);
+        mIm = mContext.getSystemService(InputManager.class);
         mSettingObserver = new SettingsObserver(mH);
 
         mPowerManagerInternal = LocalServices.getService(PowerManagerInternal.class);