release-python.nix: remove dreamed-up config option

For some reason I had the impression this option existed, but it doesn't.

Sadly `nixpkgs.config` is a freeform type attrset, that wouldn't even
bark at me, so I didn't notice this will testing.

pkgs/top-level/release-python.nix

@@ -11,7 +11,6 @@
 , # Attributes passed to nixpkgs. Don't build packages marked as unfree.
   nixpkgsArgs ? { config = {
     allowUnfree = false;
-    allowInsecure = false;
     inHydra = true;
     permittedInsecurePackages = [
       # Keep evaluating home-assistant, which is transitively affected