packagegroup-guf-tests: Remove packagegroup-guf-qt5-tests
To reduce build time and remove the Qt5 dependency of the small image, remove the packagegroup-guf-qt5-tests from the full test specification.
It became clear that adding a dependency to the recipe, even if it is not used for the resulting package, the dependencies will be built. This results in a complete qt5 build even though it is not necessary.
Also double checked that the packagegroup-guf-qt5-tests is in the relevant images.