Move 23_ 05 support

Putting 23_05 directly into the top level overlays introduced
unnecessary calculations when it is only used in one location on the IVR
system. Therefore, we only import it at the point of its use.

flake.nix

@@ -49,13 +49,9 @@
 		self,
 		...}@inputs:
 	let
-		pkg-sets = final: prev: {
-			nix23_05 = import inputs.nix23_05 { system = final.system; inherit overlays; };
-		};
 		local_overlay = import ./overlays;
 		overlays = [
 			agenix.overlays.default
-			pkg-sets
 			local_overlay
 			nurpkgs.overlay
 		];

home/hosts/ivr/default.nix

@@ -1,6 +1,10 @@
 { pkgs, lib, inputs, ...}:
 let
-	py = pkgs.nix23_05.python311.withPackages ( p: with p; [
+	nix23 = import inputs.nix23_05 {
+		inherit (pkgs.stdenv) system;
+		overlays = [ inputs.self.overlays.default ];
+	};
+	py = nix23.python311.withPackages ( p: with p; [
 		django
 		djangorestframework
 		django-rapyd-modernauth