Drop references to old security menu

roles/netbootxyz/templates/menu/boot.cfg.j2

@@ -69,7 +69,6 @@ set menu_unix 0
 set menu_freedos 0
 set menu_live 0
 set menu_live_arm 1
-set menu_security 0
 set menu_windows 0
 set menu_utils 0
 set menu_utils_arm 1
@@ -78,7 +77,6 @@ goto architectures_end
 :efi
 set menu_bsd 0
 set menu_freedos 0
-set menu_security 0
 set menu_unix 0
 goto architectures_end
 :architectures_end
@@ -116,7 +114,6 @@ set ipxe_disk netboot.xyz-packet-arm64.efi
 set menu_bsd 0
 set menu_freedos 0
 set menu_live 0
-set menu_security 0
 set menu_windows 0
 set menu_utils 0
 goto clouds_end