haskellPackages.hnix: remove now unnecessary patch

New release 0.13.0.1 introduced support with ref-tf >= 0.5, so we can
remove our patch for that purpose.

pkgs/development/haskell-modules/configuration-common.nix

@@ -174,15 +174,6 @@ self: super: {
   hnix = generateOptparseApplicativeCompletion "hnix"
     (overrideCabal super.hnix (drv: {
       doCheck = false;
-      prePatch = ''
-        # fix encoding problems when patching
-        ${pkgs.dos2unix}/bin/dos2unix hnix.cabal
-      '' + (drv.prePatch or "");
-      patches = [
-        # support ref-tf in hnix 0.12.0.1, can be removed after
-        # https://github.com/haskell-nix/hnix/pull/918
-        ./patches/hnix-ref-tf-0.5-support.patch
-      ] ++ (drv.patches or []);
     }));
 
   # Fails for non-obvious reasons while attempting to use doctest.

pkgs/development/haskell-modules/patches/hnix-ref-tf-0.5-support.patch

@@ -1,34 +0,0 @@
-diff '--color=auto' '--color=never' -r --unified hnix-0.12.0.1/hnix.cabal hnix-patched/hnix.cabal
---- hnix-0.12.0.1/hnix.cabal	2001-09-09 03:46:40.000000000 +0200
-+++ hnix-patched/hnix.cabal	2021-05-05 12:07:38.388267353 +0200
-@@ -430,7 +430,7 @@
-     , parser-combinators >= 1.0.1 && < 1.3
-     , prettyprinter >= 1.7.0 && < 1.8
-     , process >= 1.6.3 && < 1.7
--    , ref-tf >= 0.4.0 && < 0.5
-+    , ref-tf >= 0.5
-     , regex-tdfa >= 1.2.3 && < 1.4
-     , scientific >= 0.3.6 && < 0.4
-     , semialign >= 1 && < 1.2
-diff '--color=auto' '--color=never' -r --unified hnix-0.12.0.1/src/Nix/Fresh.hs hnix-patched/src/Nix/Fresh.hs
---- hnix-0.12.0.1/src/Nix/Fresh.hs	2001-09-09 03:46:40.000000000 +0200
-+++ hnix-patched/src/Nix/Fresh.hs	2021-05-05 12:07:45.841267497 +0200
-@@ -65,18 +65,3 @@
- 
- runFreshIdT :: Functor m => Var m i -> FreshIdT i m a -> m a
- runFreshIdT i m = runReaderT (unFreshIdT m) i
--
---- Orphan instance needed by Infer.hs and Lint.hs
--
---- Since there's no forking, it's automatically atomic.
--instance MonadAtomicRef (ST s) where
--  atomicModifyRef r f = do
--    v <- readRef r
--    let (a, b) = f v
--    writeRef r a
--    return b
--  atomicModifyRef' r f = do
--    v <- readRef r
--    let (a, b) = f v
--    writeRef r $! a
--    return b