Apply WindowTestRunner to RefreshRatePolicyTest

That fixes the race condition by the runner automatically locking the
window manager global lock.

Bug: 153707947
Test: atest RefreshRatePolicyTest
Change-Id: Ib2d6e76472934c90b438733835398878c1298dea

services/tests/wmtests/src/com/android/server/wm/RefreshRatePolicyTest.java

@@ -33,6 +33,7 @@ import androidx.test.filters.SmallTest;
 
 import org.junit.Before;
 import org.junit.Test;
+import org.junit.runner.RunWith;
 
 /**
  * Build/Install/Run:
@@ -40,6 +41,7 @@ import org.junit.Test;
  */
 @SmallTest
 @Presubmit
+@RunWith(WindowTestRunner.class)
 @FlakyTest
 public class RefreshRatePolicyTest extends WindowTestsBase {