Remove Required.Proto3.JsonInput.EmptyFieldMask.JsonOutput from ruby_mac too

conformance/failure_list_ruby_mac.txt

@@ -70,4 +70,3 @@ Required.Proto3.JsonInput.IgnoreUnknownJsonObject.ProtobufOutput
 Required.Proto3.JsonInput.IgnoreUnknownJsonString.ProtobufOutput
 Required.Proto3.JsonInput.IgnoreUnknownJsonTrue.ProtobufOutput
 Recommended.Proto3.JsonInput.FieldMaskInvalidCharacter
-Required.Proto3.JsonInput.EmptyFieldMask.JsonOutput