Update ci-ubuntu-2004-packages.txt
Update ci-ubuntu-2004-packages.txt

Problem occuring during the package installation : libqt4-dev
It looks, that  ubuntu doesn't support qt4 in focal release : https://packages.ubuntu.com/search?suite=focal&arch=any&searchon=names&keywords=libqt4
travis-ci/packer-templates,travis-ci/packer-templates,travis-ci/packer-templates