[Settings] Convert to getSystemService(Class<T>)

Change to getSystemService(Class<T>) to align the capability with framework
part.

Bug: 179640862
Test: local
Change-Id: I1b4812044fc4876bec6645570049a60f9470dbbd

src/com/android/settings/network/NetworkResetRestrictionChecker.java

@@ -31,7 +31,7 @@ public class NetworkResetRestrictionChecker {
 
     public NetworkResetRestrictionChecker(Context context) {
         mContext = context;
-        mUserManager = (UserManager) context.getSystemService(Context.USER_SERVICE);
+        mUserManager = context.getSystemService(UserManager.class);
     }
 
     @VisibleForTesting(otherwise = VisibleForTesting.PRIVATE)