package/chartjs: bump to version 3.9.1
https://github.com/chartjs/Chart.js/releases/tag/v3.9.1
License file has updated copyright years to 2014-2022.
Signed-off-by: Ignacy Gawędzki <ignacy.gawedzki@green-communications.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>