tests/pkg_lvgl: fix sysmon example URL.
tests/pkg_lvgl: fix sysmon example URL.

Signed-off-by: Jean Pierre Dudey <b1c1d8736f20db3fb6c1c66bb1455ed43909f0d8@jeandudey.tech>

kaspar030/RIOT,kaspar030/RIOT,ant9000/RIOT,authmillenon/RIOT,jasonatran/RIOT,authmillenon/RIOT,kaspar030/RIOT,ant9000/RIOT,miri64/RIOT,kYc0o/RIOT,ant9000/RIOT,OlegHahm/RIOT,jasonatran/RIOT,OTAkeys/RIOT,OlegHahm/RIOT,miri64/RIOT,jasonatran/RIOT,RIOT-OS/RIOT,kYc0o/RIOT,miri64/RIOT,authmillenon/RIOT,authmillenon/RIOT,kYc0o/RIOT,ant9000/RIOT,kaspar030/RIOT,OlegHahm/RIOT,RIOT-OS/RIOT,kaspar030/RIOT,miri64/RIOT,authmillenon/RIOT,OTAkeys/RIOT,RIOT-OS/RIOT,jasonatran/RIOT,OTAkeys/RIOT,kYc0o/RIOT,jasonatran/RIOT,authmillenon/RIOT,OTAkeys/RIOT,RIOT-OS/RIOT,OTAkeys/RIOT,ant9000/RIOT,OlegHahm/RIOT,kYc0o/RIOT,miri64/RIOT,OlegHahm/RIOT,RIOT-OS/RIOT