Now, it's requied.

Maybe you guys think it's necessay to make it required, but you do not know my network. My server is in intranet, I use frps to expose my service to internel. when github send webhook event to frps, the frpc client proxy the data to my probot app. maybe the client modify the data, so probot sometimes return 401 to github.

I can not use https://smee.io to proxy the data, because I access the network throw a squid proxy. besides I want github send the data to my server directly