Mark KeyguardTransitionTests#testDismissKeyguard as flaky.

Bug: 238776938
Test: Supress test.
Change-Id: Iabcca8212e03cfd6d45af7456e13ad1efa1fdd72
diff --git a/tests/framework/base/windowmanager/src/android/server/wm/KeyguardTransitionTests.java b/tests/framework/base/windowmanager/src/android/server/wm/KeyguardTransitionTests.java
index 87f4649..0a2298c4 100644
--- a/tests/framework/base/windowmanager/src/android/server/wm/KeyguardTransitionTests.java
+++ b/tests/framework/base/windowmanager/src/android/server/wm/KeyguardTransitionTests.java
@@ -36,6 +36,8 @@
 
 import android.platform.test.annotations.Presubmit;
 
+import androidx.test.filters.FlakyTest;
+
 import org.junit.Before;
 import org.junit.Test;
 
@@ -105,6 +107,7 @@
                 mWmState.getDefaultDisplayLastTransition());
     }
 
+    @FlakyTest(bugId = 238776938)
     @Test
     public void testDismissKeyguard() {
         createManagedLockScreenSession().gotoKeyguard();