feat: comment out nixpkgs-unstable, we use unstable by default

Signed-off-by: Ryan Yin <xiaoyin_c@qq.com>

home/base/core/shells/default.nix

@@ -27,7 +27,6 @@ in
   # NOTE: nushell will be launched in bash, so it can inherit all the eenvironment variables.
   programs.nushell = {
     enable = true;
-    # package = pkgs-unstable.nushell;
     configFile.source = ./config.nu;
     inherit shellAliases;
   };