Revert "let's try nushell"

This reverts commit 68d99c3696.

share/common.nix

@@ -332,7 +332,6 @@ in
     pkgs.kdePackages.neochat
     nixos-install-tools
     nmap
-    nushell
     nvme-cli
     procmail
     okteta
@@ -499,8 +498,12 @@ in
     enableMail = false;
   };
 
-  # add nushell and zsh to allowed shells
-  environment.shells = with pkgs; [ nushell zsh ];
+  # use ZSH per default
+  programs.zsh.enable = true;
+  environment.shells = with pkgs; [ zsh ];
+
+  # needed for the ZSH completion
+  environment.pathsToLink = [ "/share/zsh" ];
 
   # use micro as default terminal editor
   environment.variables.EDITOR = "micro";