Update DeviceCompatibilityModeTestJavaSnippets.java

Author: JonEckenrode

misc/src/androidTest/java/com/example/snippets/DeviceCompatibilityModeTestJavaSnippets.java

@@ -25,6 +25,7 @@
 public class DeviceCompatibilityModeTestJavaSnippets {
 
     // [START android_device_compatibility_mode_assert_isLetterboxed_java]
+    @Test
     @Rule
     public ActivityScenarioRule<MainActivity> rule = new ActivityScenarioRule<>(MainActivity.class);