changed name to official icon from iconset #4311

git-svn-id: svn://develop.studip.de/studip/trunk@31659 c5b85792-5220-0410-ad23-ed5b6b8ad999
crap. accidentally confused checked and unchecked. fixed. #4311

git-svn-id: svn://develop.studip.de/studip/trunk@31660 c5b85792-5220-0410-ad23-ed5b6b8ad999