update ar translation
update ar translation

Change-Id: I5b1c31330708c4902f795632d479714cfa28d830
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/294312
Tested-by: Service Cloud Jenkins <9144042a601061f88f1e1d7a1753ea3e2972119d@instructure.com>

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