Fixed the robo test failed in FoldLockBehaviorSettingsTest

- Use the ShadowSystemSettings instead of SystemSettings.

Fixes: 300201006
Test: atest SettingsRoboTests:com.android.settings.display.FoldLockBehaviorSettingsTest
Change-Id: I360bda0b0b35692e0eaf2060aadb791ecb9dd039

tests/robotests/src/com/android/settings/display/FoldLockBehaviorSettingsTest.java

@@ -24,13 +24,19 @@ import android.content.Context;
 import android.os.UserHandle;
 import android.provider.Settings;
 
+import com.android.settings.testutils.shadow.ShadowSystemSettings;
+
 import org.junit.Before;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.robolectric.RobolectricTestRunner;
 import org.robolectric.RuntimeEnvironment;
+import org.robolectric.annotation.Config;
 
 @RunWith(RobolectricTestRunner.class)
+@Config(shadows = {
+    ShadowSystemSettings.class,
+})
 public class FoldLockBehaviorSettingsTest {
 
     private Context mContext;