Add xqueue to the public subnet.

cloudformation_templates/edx-reference-architecture.json

@@ -2189,10 +2189,10 @@
         },
         "Subnets":[
             {
-		"Ref":"XqueueSubnet01"
+		"Ref":"PublicSubnet01"
             },
             {
-		"Ref":"XqueueSubnet02"
+		"Ref":"PublicSubnet02"
             }
         ]
       }