warnings cleanup

Author: cowtowncoder

src/test/java/com/fasterxml/jackson/databind/introspect/TestMixinMerging.java

@@ -12,10 +12,12 @@ public interface Contact {
     }
 
     static class ContactImpl implements Contact {
+        @Override
         public String getCity() { return "Seattle"; }
     }
 
     static class ContactMixin implements Contact {
+        @Override
         @JsonProperty
         public String getCity() { return null; }
     }