ncdns: Update to 2020-11-22 to remove go1.14 dep.

I've poked them to tag a new version at
https://github.com/namecoin/ncdns/issues/126, but master builds cleanly
with go1.15, so I just updated to unstable

pkgs/servers/dns/ncdns/default.nix

@@ -2,7 +2,7 @@
 
 buildGoPackage rec {
   pname = "ncdns";
-  version = "0.0.10.3";
+  version = "2020-11-22";
 
   goPackagePath = "github.com/namecoin/ncdns";
   goDeps = ./deps.nix;
@@ -10,18 +10,14 @@ buildGoPackage rec {
   src = fetchFromGitHub {
     owner = "namecoin";
     repo = "ncdns";
-    rev = "v${version}";
-    sha256 = "12q5al48mkjhgyk7z5wyklzzrdbcqhwxl79axa4gh9ld75prghbq";
+    rev = "2fa54cd3b5480dba82170ab8ecb511fbd4977c41";
+    sha256 = "0mrxbg5lmy3s281ff6nxpp03z4mqwq7h5hkqm9qy8nb280x1sx7h";
   };
 
   patches = [ ./fix-tpl-path.patch ];
 
   buildInputs = [ libcap ];
 
-  preBuild = ''
-    go generate github.com/namecoin/x509-signature-splice/...
-  '';
-
   postInstall = ''
     mkdir -p "$out/share"
     cp -r "$src/_doc" "$out/share/doc"