Update release manager tasks wiki
The wiki is here https://git.iws.uni-stuttgart.de/dumux-repositories/dumux/-/wikis/Release-Manager-Tasks There is still some points missing from the old Latex document: https://git.iws.uni-stuttgart.de/dumux-repositories/dumux-devel/-/blob/master/doc/releaseManagerTasks/releaseManagerTasks.tex. Some outdated lines might need updating too / some links might need to be fixed.