[Lokalizacija] debian-installer: URGENT update for apt-setup strings

Hi, In preparation for the release, a last minute change was made to strings belonging to the apt-setup repository. This D-I component prompts users about activation of extra package repositories. In the past, this was "volatile" and "security". Now, "volatile" disappeared and is replace by "stable-updates". So, the wording of a few tempaltes had to be changed. We did it as conservatively as possible but that still needs translation updates. I would be grateful if you could take the time and update it. Please commit the file to D-I SVN. For those of you who can't, please send it back to me. The deadline for receiving the updated translation is *Fri, 22 Jun 2012 06:46:18 +0200.*. This is SOON. Thanks in advance and sorry for this last minute urgent change.