remove korean translation

fixes CNVS-15736

it was crowd-sourced, and fell too far behind

Change-Id: I535b03b4c50c7ab65b456aba35dbb20f5788073e
Reviewed-on: https://gerrit.instructure.com/41630
QA-Review: August Thornton <august@instructure.com>
Reviewed-by: Rob Orton <rob@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
Product-Review: Cody Cutrer <cody@instructure.com>