Git commits in Moodle 3.9.7 by Shintaro Fujiwara

commit aa6c15c97544f92a673aff005d172ba154ee8125
Author: Shintaro Fujiwara <shintaro.fujiwara@gmail.com>
Date:   Fri, 26 Mar 2021 03:26:51 +0800
Tag:    v3.9.7

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