chore(users/wpcarro): drop 'exa' from NixOS systems

This is unmaintained and has been removed from nixpkgs. As an
alternative, 'eza' can be installed.

This is the last instance of 'exa' in depot, so the workaround from
the channel bump has been removed.

Change-Id: Id915260b6c969a6b2a8ecae49d3ce92285f09f71
Reviewed-on: https://cl.tvl.fyi/c/depot/+/9330
Autosubmit: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI
Reviewed-by: wpcarro <wpcarro@gmail.com>

third_party/overlays/tvl.nix

@@ -95,13 +95,6 @@ depot.nix.readTree.drvTargets {
     })
   );
 
-  # exa has been removed from nixpkgs, removing from depot in cl/9330,
-  # delete this afterwards.
-  exa = self.writeShellScriptBin "exa" ''
-    echo "'exa' has been removed from nixpkgs; please either remove it"
-    echo "from your configuration, or switch to 'eza'."
-  '';
-
   # dottime support for notmuch
   notmuch = super.notmuch.overrideAttrs (old: {
     passthru = old.passthru // {

users/wpcarro/common.nix

@@ -49,7 +49,6 @@ in
     direnv
     diskus
     emacs
-    exa
     fd
     fzf
     git