Remove nixpkgs-unstable

Also remove cachix cache for nixpkgs-unstable.

Turns out I am not using any of this on WSL, so doesn't make any sense to keep
it around.

cachix/nixpkgs-unfree.nix

@@ -1,11 +0,0 @@
-
-{
-  nix.settings = {
-    substituters = [
-      "https://nixpkgs-unfree.cachix.org"
-    ];
-    trusted-public-keys = [
-      "nixpkgs-unfree.cachix.org-1:hqvoInulhbV4nJ9yJOEr+4wxhDV4xq2d1DK7S6Nj6rs="
-    ];
-  };
-}

flake.lock

@@ -129,7 +129,7 @@
         "flake-compat": "flake-compat",
         "flake-utils": "flake-utils_2",
         "nixpkgs": [
-          "nixpkgs-unstable"
+          "nixpkgs"
         ]
       },
       "locked": {
@@ -147,26 +147,6 @@
       }
     },
     "nixpkgs": {
-      "inputs": {
-        "nixpkgs": [
-          "nixpkgs-unstable"
-        ]
-      },
-      "locked": {
-        "lastModified": 1653662045,
-        "narHash": "sha256-pTn2FPLsaHMWcP442jTN30YQZlO9K9VbWjkK6u++Q1g=",
-        "owner": "numtide",
-        "repo": "nixpkgs-unfree",
-        "rev": "d9e8ab22f97457284c676885bc874f2fa8552ea4",
-        "type": "github"
-      },
-      "original": {
-        "owner": "numtide",
-        "repo": "nixpkgs-unfree",
-        "type": "github"
-      }
-    },
-    "nixpkgs-unstable": {
       "locked": {
         "lastModified": 1656753965,
         "narHash": "sha256-BCrB3l0qpJokOnIVc3g2lHiGhnjUi0MoXiw6t1o8H1E=",
@@ -189,8 +169,7 @@
         "home-manager": "home-manager",
         "nixos-hardware": "nixos-hardware",
         "nixos-wsl": "nixos-wsl",
-        "nixpkgs": "nixpkgs",
+        "nixpkgs": "nixpkgs"
-        "nixpkgs-unstable": "nixpkgs-unstable"
       }
     },
     "utils": {

flake.nix

@@ -2,14 +2,12 @@
   description = "NixOS configuration (flake edition)";
 
   inputs = {
-    nixpkgs-unstable.url = "github:nixos/nixpkgs/nixos-unstable";
     nixpkgs = {
-      url = "github:numtide/nixpkgs-unfree";
+      url = "github:nixos/nixpkgs/nixos-unstable";
-      inputs.nixpkgs.follows = "nixpkgs-unstable";
     };
     nixos-wsl = {
       url = "github:nix-community/NixOS-WSL";
-      inputs.nixpkgs.follows = "nixpkgs-unstable";
+      inputs.nixpkgs.follows = "nixpkgs";
     };
     home-manager = {
       url = "github:nix-community/home-manager";