Revert "Use older version of jailbreak-cabal with ghcHEAD"

This reverts commit d13f7c54e3.

ghc802 is no longer in Nixpkgs as of
2f0de54ddb.

The Cabal bug that ghc802 was a workaround for was fixed in Cabal 2.2,
though, so this shouldn't be necessary any more.

Upstream bugs:
https://github.com/peti/jailbreak-cabal/issues/13
https://github.com/haskell/cabal/issues/4719

Fixes https://github.com/NixOS/nixpkgs/issues/51042.

pkgs/development/haskell-modules/configuration-ghc-head.nix

@@ -40,7 +40,7 @@ self: super: {
   xhtml = null;
 
   # jailbreak-cabal can use the native Cabal library.
-  jailbreak-cabal = pkgs.haskell.packages.ghc802.jailbreak-cabal;
+  jailbreak-cabal = super.jailbreak-cabal.override { Cabal = null; };
 
   # haddock: No input file(s).
   nats = dontHaddock super.nats;