fix pt-BR translation

refs CNVS-12126

test plan
 - change your user settings to Português do Brasil
   and verify that the new translations appear
   properly

Change-Id: If1459399df93a803be14c032ff964b179494aa0d
Reviewed-on: https://gerrit.instructure.com/32810
Reviewed-by: Jon Jensen <jon@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: August Thornton <august@instructure.com>
Product-Review: Rob Orton <rob@instructure.com>