paperless: Fix build

paperless wasn't building because django-cors-headers didn't
build anymore with the pinned django version.

I tested the paperless service (editd a few documents) and it works
fine, even with django unpinned.

pkgs/applications/office/paperless/default.nix

@@ -111,15 +111,9 @@ let
     {
       pyocr = pyocrWithUserTesseract super;
 
-      # Paperless only supports Django 2.0
-      django = customPkgs.django_2_0;
-
       # Paperless is incompatible with factory_boy >= 3
       factory_boy = customPkgs.factory_boy_2_12_0;
 
-      # The current version of django_extensions is incompatible with django 2.0
-      django_extensions = customPkgs.django_extensions_2_2_8;
-
       # These are pre-release versions, hence they are private to this pkg
       django-filter = self.callPackage ./python-modules/django-filter.nix {};
       django-crispy-forms = self.callPackage ./python-modules/django-crispy-forms.nix {};

pkgs/applications/office/paperless/python-modules/default.nix

@@ -1,24 +1,5 @@
 pyPkgs: fetchFromGitHub:
 {
-  django_2_0 = pyPkgs.django_2.overridePythonAttrs (old: rec {
-    version = "2.0.12";
-    src = pyPkgs.fetchPypi {
-      inherit (old) pname;
-      inherit version;
-      sha256 = "15s8z54k0gf9brnz06521bikm60ddw5pn6v3nbvnl47j1jjsvwz2";
-    };
-  });
-
-  django_extensions_2_2_8 = pyPkgs.django_extensions.overridePythonAttrs (old: rec {
-    version = "2.2.8";
-    src = fetchFromGitHub {
-      owner = old.pname;
-      repo = old.pname;
-      rev = version;
-      sha256 = "1gd3nykwzh3azq1p9cvgkc3l5dwrv7y86sfjxd9llbyj8ky71iaj";
-    };
-  });
-
   factory_boy_2_12_0 = pyPkgs.factory_boy.overridePythonAttrs (old: rec {
     version = "2.12.0";
     src = pyPkgs.fetchPypi {