Backend tweaks

[LachlanStuart]

A bunch of small changes, mainly dev experience improvements.

• Disabled sci-test as it has just been continually failing on master branch
• Remove auto-publishing of python-client, as we always manually publish it
• Increase email verification tokens' expiry time (fixes Raise email verification timeout to 60 minutes #780)
• Turn off slack notifications for successful INDEX/UPDATE/CLASSIFY_OFF_SAMPLE messages. Failures are still reported, though these processes virtually never fail.
• Change the Lithops retry logic to always retry, not just for stalls. I did this because I've seen ~3 datasets that failed on their first attempt but succeeded on retry since the Lithops deployment.
• Add killasgroup to the sm-lithops-daemon supervisor file. documented here. This is a small mitigation for Fix Lithops zombie processes issue #795 , which should hopefully mean that stalled background processes spawned by multiprocessing don't need to be manually removed