haskellPackages.gitit: Remove obsolete patch

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

···
   # $HOME, which we don't have in our build sandbox.
   cabal-install-parsers = dontCheck super.cabal-install-parsers;
 
-  # jailbreak and patch (for pandoc >= 2.12) ensure compilation with newer dependencies.
-  # can both be removed at the next release (current is 0.13.0.0)
-  gitit = doJailbreak (appendPatch super.gitit
-    (pkgs.fetchpatch {
-      url = "https://github.com/jgm/gitit/commit/e8c9d94be332e2f73de9b0eee222a2a09f191faf.patch";
-      sha256 = "1rl2c3sz8cd2c3qwv9b640853s4bblcknvfv29k472wqhs62mwz1";
-      includes = [ "src/**" ];
-    }));
+  # 2021-08-18: Erroneously  claims that it needs a newer HStringTemplate (>= 0.8.8) than stackage.
+  gitit = doJailbreak super.gitit;
 
   # Test suite requires database
   persistent-mysql = dontCheck super.persistent-mysql;