Update metadata.graphqls

Delete the parameter named duration in searchService method. Do not need duration to query service by exact-match.

metadata.graphqls

@@ -51,7 +51,7 @@ extend type Query {
     # Service related meta info.
     getAllServices(duration: Duration!): [Service!]!
     searchServices(duration: Duration!, keyword: String!): [Service!]!
-    searchService(duration: Duration!, serviceCode: String!): Service
+    searchService(serviceCode: String!): Service
 
     # Service intance query
     getServiceInstances(duration: Duration!, id: ID!): [ServiceInstance!]!