Remove unused builder

This will cost time for no good reason.

Change-Id: I8e3f3e4cc597dd7ab03cb0d4afa8fdf134a65518
diff --git a/aos/events/simulated_network_bridge.cc b/aos/events/simulated_network_bridge.cc
index 020abc9..93a90ed 100644
--- a/aos/events/simulated_network_bridge.cc
+++ b/aos/events/simulated_network_bridge.cc
@@ -149,9 +149,6 @@
     if (timestamp_logger_) {
       flatbuffers::FlatBufferBuilder fbb;
         fbb.ForceDefaults(true);
-      aos::Sender<RemoteMessage>::Builder builder =
-          timestamp_logger_->MakeBuilder();
-
       // Reset the filter every time the UUID changes.  There's probably a more
       // clever way to do this, but that means a better concept of rebooting.
       if (server_status_->BootUUID(destination_node_index_) !=