doas: 6.8 -> 6.8.1

Most notably, addresses CVE-2019-25016.

https://github.com/Duncaen/OpenDoas/releases/tag/v6.8.1

https://github.com/Duncaen/OpenDoas/compare/v6.8...v6.8.1

pkgs/tools/security/doas/default.nix

···
-{ stdenv
-, lib
+{ lib
+, stdenv
 , fetchFromGitHub
 , bison
 , pam
···
 
 stdenv.mkDerivation rec {
   pname = "doas";
-  version = "6.8";
+  version = "6.8.1";
 
   src = fetchFromGitHub {
     owner = "Duncaen";
     repo = "OpenDoas";
     rev = "v${version}";
-    sha256 = "1dlwnvy8r6slxcy260gfkximp1ms510wdslpfq9y6xvd2qi5izcb";
+    sha256 = "sha256-F0FVVspGDZmzxy4nsb/wsEoCw4eHscymea7tIKrWzD0=";
   };
 
   # otherwise confuses ./configure