fix unit test.

"200" in API Response is a String, so it is under quotes in JSON and YAML
diff --git a/geronimo-openapi-impl/src/test/java/org/apache/geronimo/microprofile/openapi/impl/serialization/SerializationTest.java b/geronimo-openapi-impl/src/test/java/org/apache/geronimo/microprofile/openapi/impl/serialization/SerializationTest.java
index 4adb96a..c245f35 100644
--- a/geronimo-openapi-impl/src/test/java/org/apache/geronimo/microprofile/openapi/impl/serialization/SerializationTest.java
+++ b/geronimo-openapi-impl/src/test/java/org/apache/geronimo/microprofile/openapi/impl/serialization/SerializationTest.java
@@ -46,7 +46,7 @@
         try (final Jsonb jsonb = JsonbBuilder.create()) {
             assertEquals("{\"default\":{\"description\":\"test\"},\"200\":{\"description\":\"ok\"}}", jsonb.toJson(responses));
         }
-        assertEquals("---\ndefault:\n  description: \"test\"\n200:\n  description: \"ok\"\n", Yaml.getObjectMapper().writeValueAsString(responses));
+        assertEquals("---\ndefault:\n  description: \"test\"\n\"200\":\n  description: \"ok\"\n", Yaml.getObjectMapper().writeValueAsString(responses));
     }
 
     @Test