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

conformance/failure_list_ruby_mac.txt

diff --git a/conformance/failure_list_ruby_mac.txt b/conformance/failure_list_ruby_mac.txt
index 86a5da1..3114cba 100644
--- a/conformance/failure_list_ruby_mac.txt
+++ b/conformance/failure_list_ruby_mac.txt
@@ -70,4 +70,3 @@
 Required.Proto3.JsonInput.IgnoreUnknownJsonString.ProtobufOutput
 Required.Proto3.JsonInput.IgnoreUnknownJsonTrue.ProtobufOutput
 Recommended.Proto3.JsonInput.FieldMaskInvalidCharacter
-Required.Proto3.JsonInput.EmptyFieldMask.JsonOutput