Re-enable parallel builds in CI
thanks @WillAyd. @meeseeksdev backport 2.0.x Thanks for review. Don't think we can backport this without #51525 as well though My bad, forgot about that one. I don't think we should backport that one, since it changes a lot of the C extensions making it pretty risky. Yea I'm ok without it being backported. We've lived this long without it on 2.0 By the way I couldn't believe how easy this was to re-enable. Kudos @lithomas1 or whoever has been consolidating those CI jobs - super cool