Author: Simey Lameze
MDL-66604 mod_forum: add missing exportforum lang string
Part of MDL-66075.
http://git.moodle.org/gw?p=moodle.git;a=commit;h=30eeb2a528bb1485cdd2862122999863ca6720fe
http://github.com/moodle/moodle/commit/30eeb2a528bb1485cdd2862122999863ca6720fe
+ 3.8 en [forum:exportforum,mod_forum]