Add channel for rubocop 1.34.1

[hampld]

rubocop/rubocop just released version 1.34.1.

We would like our projects with CodeClimate to stay up to date with this, but it looks like the 1.34.1 channel has not been made available yet according to the channel list.

[vietqhoang]

Just want to add as a general comment in regards to channels. It would be great to see channels of the latest versions be made available more quickly.

We also like our projects with CodeClimate to stay up-to-date with RuboCop, but the lack of available channels for new versions is roadblocking us. I understand the beta channel tends to have the latest Rubocop version. However, since the beta channel isn't locked to a version, it does not give us control to lock into a Rubocop version on our projects.

[kristof-mattei]

Also worth pointing out here is that channel: rubocop-1-31-0 doesn't work with the online version. It only works on the CLI. See https://github.com/codeclimate/codeclimate-rubocop/pull/318#issuecomment-1202978992