Relax hmi-switch-graphical-applications to use any application

The test hmi-switch-graphical-applications requests to open Fonts application
which is installed by default in HMI images via Flatpak, but not installed
on SDK. Since the test can be run with any graphical application, relax
it and mention Fonts only as a suggestion.

Signed-off-by: Walter Lozano <walter.lozano@collabora.com>