docs(gateway): remove store measurement arrow from sequence diagram

broker -> db storage is handled by the database manager, not the gateway

doc_resources/gateway/sequence_data_collection.puml

@@ -32,7 +32,6 @@ else
                 gw -> gw : add UTC timestamp
                 gw -> broker : publish JSON\n{gateway_id}/{mac}/update
                 broker --> gw : on_publish confirmed
-                broker -> db : store measurement
             end
         end
     end