fix some rspec deprecation warnings

refs CNVS-16239

Change-Id: Id706ca284f2f8754a889949a60bca30ace46bd99
Reviewed-on: https://gerrit.instructure.com/42812
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Jeremy Stanley <jeremy@instructure.com>
Product-Review: Braden Anderson <braden@instructure.com>
QA-Review: Braden Anderson <braden@instructure.com>