Author: Shamim Rezaie
MDL-71163 mod_assign: remove duplicate available from and due date info
http://git.moodle.org/gw?p=moodle.git;a=commit;h=1abf669d995b4f157fd1b9100108713d2819d30d
http://github.com/moodle/moodle/commit/1abf669d995b4f157fd1b9100108713d2819d30d
+ 3.11 en [activitydate:submissionsdue,mod_assign]
+ 3.11 en [activitydate:submissionsopen,mod_assign]
+ 3.11 en [activitydate:submissionsopened,mod_assign]