comm_info_reply should not be sent on IOPub

[twavv]

IJulia sends the comm_info_reply message (in response to comm_info_request) on the IOPub channel, but it should be sent as a reply on the shell channel.

https://jupyter-client.readthedocs.io/en/stable/messaging.html#comm-info

[stevengj]

Whoops, can you make a PR?

[twavv]

Sure. :)

Is there any way I could get commit permissions for the repo? I'm happy to go through the PR process and whatnot, but there have been a number of things languishing for a while (e.g., #859, #946)