Drop cabal-experimental input, use regular cabal for all shells
The cabal-experimental input (stable-haskell/cabal cross-compile branch) was used for withGHCTooling shells. The pinned version (Apr 2025) has hackage-security bounds incompatible with GHC 9.10+/9.12+ (ghc-prim >= 0.12), causing IFD plan resolution failures. The newer version (Aug 2025) fixes that but regresses shared library handling, breaking downstream CI. Simplify by using the regular cabal input for all shell variants.