update ar translation
update ar translation

Change-Id: Ia1a96c8fd0d68cb43c5114981420f8859965ba00
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/272654
Tested-by: Service Cloud Jenkins <9144042a601061f88f1e1d7a1753ea3e2972119d@instructure.com>

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