tests: patched nixpkgs no longer needed

tests/default.nix

@@ -3,40 +3,10 @@ let
   inherit (self.inputs) nixos;
   inherit (self.nixosConfigurations.NixOS.config.lib) testModule specialArgs;
 
-  # current release 20.09 does not support the specialArgs required for us
-  # to use tests as we would normally use hosts. Using the "testing-python.nix"
-  # from the override flake would build the test-vm from an unstable os
-  # different than the one our systems are running. Instead simply patch nixpkgs
-  # to include the updated version. This can be removed in the next release
-  patchedNixpkgs =
-    pkgs.stdenv.mkDerivation {
-      name = "nixpkgs-patched";
-
-      src = nixos;
-      patches = [ ./0004-nixos-testing-Add-support-for-specialArgs.patch ];
-
-      dontBuild = true;
-      dontFixup = true;
-
-      versionSuffix = "pre${
-    if nixos ? lastModified
-    then builtins.substring 0 8 (nixos.lastModifiedDate or nixos.lastModified)
-    else toString nixos.revCount}.${nixos.shortRev or "dirty"}";
-
-      configurePhase = ''
-        echo -n $VERSION_SUFFIX > .version-suffix
-        echo -n ${nixos.rev or nixos.shortRev or "dirty"} > .git-revision
-      '';
-
-      installPhase = ''
-        cp -r $PWD $out
-      '';
-    };
-
   mkTest =
     let
       nixosTesting =
-        (import "${patchedNixpkgs}/nixos/lib/testing-python.nix" {
+        (import "${nixos}/nixos/lib/testing-python.nix" {
           inherit (pkgs.stdenv.hostPlatform) system;
           inherit specialArgs;
           inherit pkgs;