update ar translation
update ar translation

Change-Id: I96c5285fa9387e945f84ea6df6fb2e331e952757
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/288167
Tested-by: Service Cloud Jenkins <9144042a601061f88f1e1d7a1753ea3e2972119d@instructure.com>

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