update Cabal in both NixPkgs and hackage.nix

Author: peterbecich

flake.lock

@@ -4,7 +4,7 @@
       url = "github:input-output-hk/hackage.nix";
       flake = false;
     };
-    nixpkgs.follows = "haskellNix/nixpkgs-unstable";
+    nixpkgs.url = "github:peterbecich/nixpkgs/update-hackage";
     haskellNix = {
       url = "github:input-output-hk/haskell.nix";
       inputs.hackage.follows = "hackageNix";