haskell-esqueleto: drop the markBroken for ghc 8.4.1

Although accurate, the override causes evaluation errors that serve little
purpose but poison our dashboard at [1].

[1] https://hydra.nixos.org/jobset/nixpkgs/haskell-updates

pkgs/development/haskell-modules/configuration-ghc-8.4.x.nix

···
   unix = null;
   xhtml = null;
 
-  # https://github.com/bitemyapp/esqueleto/issues/77
-  esqueleto = markBrokenVersion "2.5.3" super.esqueleto;
-
   # Need newer version.
   haskell-src = super.haskell-src_1_0_3_0;