live: Do not allow running non-GUI d-i

config/bootloaders/isolinux.live/install.cfg

@@ -1,11 +1,5 @@
-label install
-	menu label ^Install
-	linux /install/vmlinuz
-	initrd /install/initrd.gz
-	append vga=788 @APPEND_INSTALL@ --- quiet
-
 label installgui
-	menu label ^Graphical install
+	menu label ^Install
 	linux /install/gtk/vmlinuz
 	initrd /install/gtk/initrd.gz
 	append video=vesa:ywrap,mtrr vga=788 @APPEND_INSTALL@ --- quiet