chore(nixbuild): remove deprecated shellInit for SSH sessions

- Deleted `environment.shellInit` previously used for Nix path initialization in SSH sessions.
- Path initialization is now fully handled by `programs.fish.loginShellInit` for consistency across environments.

systems/nixbuild.nix

@@ -1,6 +1,4 @@
-{ lib, pkgs, ... }:
-
-with lib.metacfg;
+{ ... }:
 {
   nix.distributedBuilds = true;
 
@@ -44,12 +42,6 @@ with lib.metacfg;
   };
 
   # Ensure Nix is in PATH for SSH sessions
-  environment.shellInit = ''
-    if [ -e /nix/var/nix/profiles/default/etc/profile.d/nix-daemon.sh ]; then
-      . /nix/var/nix/profiles/default/etc/profile.d/nix-daemon.sh
-    fi
-  '';
-
   programs.fish.loginShellInit = ''
     set -gx PATH /nix/var/nix/profiles/default/bin $PATH
     set -gx PATH /run/current-system/sw/bin $PATH