Unpin slackclient in automation
This pin was causing problems when building our images: https://dagster.phacility.com/P103. I don't think we actually need this pin, because slackclient is just used to send the message to #general when releasing.
This diff also adds installing automation to make dev_install
Test Plan: none
Reviewers: alangenfeld, johann, nate, rexledesma
Reviewed By: rexledesma
Differential Revision: https://dagster.phacility.com/D4720