Stops @Ignore-ing a11y robotests.

Our team is trying to determine the state of our tests in automation,
which is tough to do when some tests are skipped completely.

A11y SettingsRobotests are currently run only in postsubmit, so even
if the Ignored tests fail it should not cause presubmit issues.

Bug: 279082331
Test: Use go/abtd to ensure tests run (and some fail)
Change-Id: I767b25427e748b7e94ab05e81a2f645f8b6279cf

tests/robotests/src/com/android/settings/accessibility/AccessibilityButtonFragmentTest.java

@@ -39,7 +39,6 @@ import com.android.settings.testutils.XmlTestUtils;
 import com.android.settings.testutils.shadow.ShadowFragment;
 
 import org.junit.Before;
-import org.junit.Ignore;
 import org.junit.Rule;
 import org.junit.Test;
 import org.junit.runner.RunWith;
@@ -53,7 +52,6 @@ import org.robolectric.annotation.Config;
 import java.util.List;
 
 /** Tests for {@link AccessibilityButtonFragment}. */
-@Ignore
 @Config(shadows = ShadowFragment.class)
 @RunWith(RobolectricTestRunner.class)
 public class AccessibilityButtonFragmentTest {