python3Packages.django-rest-registration: fix src.rev

pkgs/development/python-modules/django-rest-registration/default.nix

···
   src = fetchFromGitHub {
     owner = "apragacz";
     repo = pname;
-    rev = "refs/tags/v${version}";
+    rev = "refs/tags/${version}";
     hash = "sha256-JoIeVjl5s60ilq9kU28Jo+GaYRKU61hoqy1GzYmMdZQ=";
   };