Ryan Scott authored Mar 05, 2021 and Marge Bot committed Mar 09, 2021

Now that GHC 9.0.1 is released, it is time to drop support for bootstrapping
with GHC 8.8, as we only support building with the previous two major GHC
releases. As an added bonus, this allows us to remove several bits of CPP that
are either always true or no longer reachable.