Well this makes things mucho easier then
If the addon isn't used in that mission anymore, just
remove it manually by editing the mission.sqm from the addons
and/or auto addons section - load it up into the mission editor -
save it again by export to sp or mp - and whooop it should be
gone.
P.S: to make sure it isn't used anywhere in that map, you should
also preview the mission once before exporting it.
Also note that you cannot overwrite an already existing pbo file
when exporting the mission, but when changing the mission name at exporting you need to take care that you don't change
the mission name different to your sqm version, or there wouldn't
be scripts briefings or other files than the sqm become exported.
Therefore you need to remove/delete/backup the previous pbo
file before doing so.
hope this helps
~S~ CD