Make webmock allow requests to webpack too

spec/support/webmock.rb

@@ -8,7 +8,11 @@ def webmock_allowed_hosts
     if ENV.key?('ELASTIC_URL')
       hosts << URI.parse(ENV['ELASTIC_URL']).host
     end
-  end.uniq
+
+    if Gitlab.config.webpack&.dev_server&.enabled
+      hosts << Gitlab.config.webpack.dev_server.host
+    end
+  end.compact.uniq
 end
 
 WebMock.disable_net_connect!(allow_localhost: true, allow: webmock_allowed_hosts)