code: public void removeProxyServer(ProxyServer proxyServer) {
          proxyServers.remove(proxyServer);
          extensionHooks.values().forEach(extHook -> unhookProxyServer(extHook, proxyServer));
      }
docs: Removes the given proxy server.
  
  @param proxyServer the proxy server to remove, must not be null.
  @since TODO add version
  @see #addProxyServer(ProxyServer)