MissingH: use a version appropriate to our compiler

If you actually look at the changelog for 1.4.2.1, you'll see that it
mentions that it was only intended for ghc-7.0.4, which is why it has
a dependency on an inconveniently old version of `unix`, which
is *also* hidden behind a flag, so that we can't jailbreak it (per
https://github.com/peti/jailbreak-cabal/issues/15).

So the right thing to do would appear to me to be to override our
default version to 1.4.2.0, until such time as the maintainer makes a
newer release.

`ConfigFile` was collateral damage, so unmark it broken, as well as
`MissingH` itself.

pkgs/development/haskell-modules/configuration-hackage2nix.yaml

@@ -67,6 +67,8 @@ core-packages:
 # comment saying "# LTS Haskell x.y". Any changes after that commend will be
 # lost the next time `update-stackage.sh` runs.
 default-package-overrides:
+  # This was only intended for ghc-7.0.4, and has very old deps, one hidden behind a flag
+  - MissingH ==1.4.2.0
   # for cabal-install-3.0.0.0
   - hackage-security >=0.5.2.2 && <0.6
   # pandoc-2.9 does not accept the 0.3 version yet
@@ -3753,7 +3755,6 @@ broken-packages:
   - confide
   - config-parser
   - config-select
-  - ConfigFile
   - ConfigFileTH
   - Configger
   - configifier
@@ -7422,7 +7423,6 @@ broken-packages:
   - miss
   - miss-porcelain
   - missing-py2
-  - MissingH
   - MissingPy
   - mix-arrows
   - mixed-strategies