remove TODO

@jbenet when returning values for records, when would it make sense to
also return providers for the records?

routing/grandcentral/server.go

@@ -52,7 +52,6 @@ func (s *Server) handleMessage(
 			return "", nil
 		}
 		response.Record = rawRecord
-		// TODO before merging: if we know any providers for the requested value, return those.
 		return p, response
 
 	case dhtpb.Message_PUT_VALUE: