update pt-BR translation
update pt-BR translation

Change-Id: I8c8c7170c7e72c106613a3d94da8a43771273b18
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/274479
Tested-by: Service Cloud Jenkins <9144042a601061f88f1e1d7a1753ea3e2972119d@instructure.com>

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