update ar translation
update ar translation

Change-Id: I640348d63e6afb7446d79ef85004868c429e347b
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/293271
Tested-by: Service Cloud Jenkins <9144042a601061f88f1e1d7a1753ea3e2972119d@instructure.com>

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