Fix client advertised channels not being updated on unadvertise (#132)

**Public-Facing Changes**
None


**Description**
When a client unadvertised a channel, we did not update the client's
publications list, leading to lots of
`Ignoring client unadvertisement from ... for unknown channel ...,`
messages once the client disconnected

foxglove_bridge_base/include/foxglove_bridge/websocket_server.hpp

@@ -763,6 +763,11 @@ inline void Server<ServerConfiguration>::handleTextMessage(ConnHandle hdl, const
           continue;
         }
         clientPublications.erase(channelIt);
+        if (const auto advertisedChannelIt = clientInfo.advertisedChannels.find(channelId) !=
+                                             clientInfo.advertisedChannels.end()) {
+          clientInfo.advertisedChannels.erase(advertisedChannelIt);
+        }
+
         if (_clientUnadvertiseHandler) {
           _clientUnadvertiseHandler(channelId, hdl);
         }