* tests: use keycode_string feature
With a proper keycode to string implementation in qmk there is no need
to use the unit tests only implementation anymore.
Signed-off-by: Stefan Kerkmann <karlk90@pm.me>
* tests: remove keycode_util feature
This feature is no longer used as we switched the tests to the
keycode string implementation.
Signed-off-by: Stefan Kerkmann <karlk90@pm.me>
