Author: Nathan Nguyen
MDL-69613 gradereport: confirm message if override none is selected
http://git.moodle.org/gw?p=moodle.git;a=commit;h=ee1f0fb18ab0055ff47d64977e2e12921e5e7ed8
http://github.com/moodle/moodle/commit/ee1f0fb18ab0055ff47d64977e2e12921e5e7ed8
+ 4.0 en [overridenoneconfirm,gradereport_singleview]