removed "ubiquity/keep-installed" from preseed

Old keep-install command leads to installation of ALL packages during
the installation when "download updates while installing" is selected.

assemble_image.sh

@@ -37,7 +37,8 @@ fill_grub_config_template "$img2" "$workspace/part_files/boot/grub/grub.cfg"
 #./create_offlinerepo.sh "$workspace/part_files/archives" "$img1" $(grep '^[^#]' packages | cut -d'|' -f 2)
 #./create_offlinerepo.sh "$workspace/part_files/archives" "$img2" $(grep '^[^#]' packages | cut -d'|' -f 2)
 cp packages "$workspace/part_files/packages"
-echo "ubiquity ubiquity/keep-installed string $(grep '^[^#]' packages | cut -d'|' -f 2 | tr '\n' ' ')" >> "$workspace/part_files/preseed/lip.seed"
+# The following command is dangerous: If offline repo is missing and "download updates while installing" is selected (default), this will install ALL listed packages during the installation.
+#echo "ubiquity ubiquity/keep-installed string $(grep '^[^#]' packages | cut -d'|' -f 2 | tr '\n' ' ')" >> "$workspace/part_files/preseed/lip.seed"
 
 rm -f "$workspace/part.img"
 truncate -s "$image_size" "$workspace/part.img"