Revert "nixos: make GIO_EXTRA_MODULES a session variable"

This reverts commit abfcb79abf3ba32eb4719c48915a143370093fb7.

Fixes: https://github.com/NixOS/nixpkgs/issues/149539

nixos/modules/programs/dconf.nix

···
     environment.systemPackages = [ pkgs.dconf ];
 
     # Needed for unwrapped applications
-    environment.sessionVariables.GIO_EXTRA_MODULES = mkIf cfg.enable [ "${pkgs.dconf.lib}/lib/gio/modules" ];
+    environment.variables.GIO_EXTRA_MODULES = mkIf cfg.enable [ "${pkgs.dconf.lib}/lib/gio/modules" ];
   };
 
 }

nixos/modules/services/desktops/gnome/glib-networking.nix

···
 
     systemd.packages = [ pkgs.glib-networking ];
 
-    environment.sessionVariables.GIO_EXTRA_MODULES = [ "${pkgs.glib-networking.out}/lib/gio/modules" ];
+    environment.variables.GIO_EXTRA_MODULES = [ "${pkgs.glib-networking.out}/lib/gio/modules" ];
 
   };
 

nixos/modules/services/desktops/gvfs.nix

···
     services.udev.packages = [ pkgs.libmtp.bin ];
 
     # Needed for unwrapped applications
-    environment.sessionVariables.GIO_EXTRA_MODULES = [ "${cfg.package}/lib/gio/modules" ];
+    environment.variables.GIO_EXTRA_MODULES = [ "${cfg.package}/lib/gio/modules" ];
 
   };