add an auto-generated comment to language yml files

Change-Id: Ib5edd010f8a6268d2ece5857ea6d5eca383c6d6a
Reviewed-on: https://gerrit.instructure.com/39786
Reviewed-by: Jacob Fugal <jacob@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
Product-Review: Brian Palmer <brianp@instructure.com>
QA-Review: Brian Palmer <brianp@instructure.com>