Update the devshell for jj use instead of git

devshells/default/default.nix

@@ -1,10 +1,9 @@
-{pkgs, ...}:
+{ pkgs, ... }:
 pkgs.mkShell {
   name = "default";
 
   buildInputs = builtins.attrValues {
-    inherit
-      (pkgs)
+    inherit (pkgs)
       git
       vim
       nixos-anywhere
@@ -14,6 +13,6 @@ pkgs.mkShell {
   };
 
   shellHook = ''
-    git pull
+    jj fetch
   '';
 }