Revert "Switch to unstable by default"

This reverts commit 3c7877776e.

Slack was broken when using the unstable version of nixpkgs.

system/shared/home-manager-packages.nix

@@ -1,5 +1,7 @@
 { inputs, pkgs, ... }:
-
+let
+  pkgsUnstable = inputs.nixpkgs-unstable.legacyPackages."${pkgs.system}";
+in
 with pkgs; [
   awscli2
   bottom
@@ -24,9 +26,9 @@ with pkgs; [
   lua
   mysql
   neofetch
+  pkgsUnstable.rustywind
   pv
   ripgrep
-  rustywind
   terraform
   tldr
   tree