Author: Simey Lameze
MDL-66360 lang: fix typo on gradenotificationsubjects string
http://git.moodle.org/gw?p=moodle.git;a=commit;h=86ea1d8375ef2537561c7e71cb96bf968bb0f37f
http://github.com/moodle/moodle/commit/86ea1d8375ef2537561c7e71cb96bf968bb0f37f
+ 3.8 en [gradenotificationsubject,core_grades]