Sort imports

Having consistent import order will reduce chance of merge
conflict between internal and external master

Test: rebuild
Change-Id: I0b1a170967ddcce7f388603fd521f6ed1eeba30b

src/com/android/settings/development/featureflags/FeatureFlagPersistent.java

@@ -21,12 +21,12 @@ import android.os.SystemProperties;
 import android.text.TextUtils;
 import android.util.FeatureFlagUtils;
 
+import androidx.annotation.VisibleForTesting;
+
 import com.android.settings.core.FeatureFlags;
 
 import java.util.HashSet;
 
-import androidx.annotation.VisibleForTesting;
-
 /**
  * Helper class to get feature persistent flag information.
  */