Revert "removed contact schema ref"

This reverts commit 9cc0f88.

Author: vaibhavjainv

msk-lambda-schema-avro-java-sam/MSKAndKafkaClientEC2.yaml

@@ -1289,4 +1289,9 @@ Outputs:
     Description: The Topic to use for the Java Lambda Function
     Value: !Ref KafkaTopicForLambda
     Export:
-      Name: !Sub "${AWS::StackName}-KafkaTopicForLambda"
+      Name: !Sub "${AWS::StackName}-KafkaTopicForLambda"
+  ContactSchemaArn:
+    Description: ARN of the Contact Schema Registry
+    Value: !Ref ContactSchema
+    Export:
+      Name: !Sub "${AWS::StackName}-ContactSchemaArn"