prevent self-XSS when rating an app, fixes CNVS-17657

low severity, as you can only xss yourself

test plan: see CNVS-17657

Change-Id: I4ab01fab4a6cec67da0bd83999eff9080dee005b
Reviewed-on: https://gerrit.instructure.com/46284
Product-Review: Bracken Mosbacker <bracken@instructure.com>
Reviewed-by: Bracken Mosbacker <bracken@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: Caleb Guanzon <cguanzon@instructure.com>