eval-config: remove compatibility shims

20.03 and 22.03 are both deprecated and no longer work with nix-darwin.

eval-config.nix

@@ -42,24 +42,14 @@ let
     };
   };
 
-  libExtended = lib.extend (self: super: {
-    # Added in nixpkgs #136909, adds forward compatibility until 22.03 is deprecated.
-    literalExpression = super.literalExpression or super.literalExample;
-    literalDocBook = super.literalDocBook or super.literalExample;
-  });
-
-  eval = libExtended.evalModules (builtins.removeAttrs args [ "lib" "inputs" "pkgs" "system" ] // {
+  eval = lib.evalModules (builtins.removeAttrs args [ "lib" "inputs" "pkgs" "system" ] // {
     modules = modules ++ [ argsModule pkgsModule ] ++ baseModules;
     specialArgs = { modulesPath = builtins.toString ./modules; } // specialArgs;
   });
-
-  # Was moved in nixpkgs #82751, so both need to be handled here until 20.03 is deprecated.
-  # https://github.com/NixOS/nixpkgs/commits/dcdd232939232d04c1132b4cc242dd3dac44be8c
-  _module = eval._module or eval.config._module;
 in
 
 {
-  inherit (_module.args) pkgs;
+  inherit (eval._module.args) pkgs;
   inherit (eval) options config;
 
   system = eval.config.system.build.toplevel;