Replace @ReflectiveTestCase() with @reflectiveTest.

pkg/analysis_server/test/integration/asynchrony_test.dart

Index: pkg/analysis_server/test/integration/asynchrony_test.dart
diff --git a/pkg/analysis_server/test/integration/asynchrony_test.dart b/pkg/analysis_server/test/integration/asynchrony_test.dart
index 0194facb18f42cf6c2eeefe7578f61b9d085c7ed..ad4cd07b673bad2dddd23475c8dceb97a02eedcc 100644
--- a/pkg/analysis_server/test/integration/asynchrony_test.dart
+++ b/pkg/analysis_server/test/integration/asynchrony_test.dart
@@ -24,7 +24,7 @@ main() {
  * Once enough commands have been sent, we begin reading from the server's
  * output buffer, and verify that it responds to the last command.
  */
-@ReflectiveTestCase()
+@reflectiveTest
 class AsynchronyIntegrationTest {
   /**
    * Number of messages to queue up before listening for responses.