Enable COUNT integration tests, now that backend support has rolled out (#4163)

Author: dconeybe

firebase-firestore/src/androidTest/java/com/google/firebase/firestore/CountTest.java

@@ -30,19 +30,12 @@
 import androidx.test.ext.junit.runners.AndroidJUnit4;
 import com.google.firebase.firestore.testutil.IntegrationTestUtil;
 import org.junit.After;
-import org.junit.Before;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 
 @RunWith(AndroidJUnit4.class)
 public class CountTest {
 
-  @Before
-  public void setUp() {
-    // TODO(b/243368243): Remove this once backend is ready to support count.
-    org.junit.Assume.assumeTrue(BuildConfig.USE_EMULATOR_FOR_TESTS);
-  }
-
   @After
   public void tearDown() {
     IntegrationTestUtil.tearDown();