leocad: 21.03 -> 21.06

Also update the ldraw-based library to the latest snapshot available
from archive.org (20210705153544).

pkgs/applications/graphics/leocad/default.nix

···
 
 let
   parts = fetchurl {
-    url = "https://web.archive.org/web/20190715142541/https://www.ldraw.org/library/updates/complete.zip";
+    url = "https://web.archive.org/web/20210705153544/https://www.ldraw.org/library/updates/complete.zip";
     sha256 = "sha256-PW3XCbFwRaNkx4EgCnl2rXH7QgmpNgjTi17kZ5bladA=";
   };
 
 in
 mkDerivation rec {
   pname = "leocad";
-  version = "21.03";
+  version = "21.06";
 
   src = fetchFromGitHub {
     owner = "leozide";
     repo = "leocad";
     rev = "v${version}";
-    sha256 = "sha256-69Ocfk5dBXwcRqAZWEP9Xg41o/tAQo76dIOk9oYhCUE=";
+    sha256 = "1ifbxngkbmg6d8vv08amxbnfvlyjdwzykrjp98lbwvgb0b843ygq";
   };
 
   nativeBuildInputs = [ qmake qttools ];