Git commits in Moodle 3.10.x by Shintaro Fujiwara

commit c906a33e1e3c083f5f1daf1cc43594b08e726f14
Author: Shintaro Fujiwara <shintaro.fujiwara@gmail.com>
Date:   Fri, 26 Mar 2021 09:31:40 +0800
Tag:    v3.10.4

MDL-69304 gradeimport_csv: Validate if the user id is numerical.