Remove some of the cpu resouce from the CI

After our recent resource usage changes, the CI requests had actually become larger than our defaults.

The defaults have been based off https://gitlab.com/charts/gitlab/blob/master/doc/architecture/resource-usage.md

And in these three cases, what we are now requesting is lower than what we had here in CI. (300m for unicorn, 50m for sidekiq, and 0 for shell)