https://www.stackage.org/ lists the latest LTS snapshot for any GHC
version which, on the flipside, lets us discover which versions don't
have a corresponding LTS snapshot. There is really no reason to keep
around GHCs that only appeared in some nightly snapshot way back.
haskell.compiler.ghc924: remove at 9.2.4
haskell.compiler.ghc942: remove at 9.4.2
haskell.compiler.ghc943: remove at 9.4.3
haskell.compiler.ghc944: remove at 9.4.4
haskell.compiler.ghc962: remove at 9.6.2