package/qt5: remove menu comment about deprecated modules

As now the Qt version is configurable to simplify the menu display
logic we remove the menu comment about deprecated modules and
indicate it in the relevant modules' help text instead, and also
mention in the help text if a package's tech preview status has been
changed between Qt 5.6 and Qt 5.8

Signed-off-by: Zoltan Gyarmati <mr.zoltan.gyarmati@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>