Fix errors in context_modules_spec.rb

Change-Id: Icb907b3498882bde9ce34d52412a899a464ef8bc
Reviewed-on: https://gerrit.instructure.com/44129
Tested-by: Jenkins <jenkins@instructure.com>
Product-Review: Matt Fairbourn <mfairbourn@instructure.com>
Reviewed-by: Matt Fairbourn <mfairbourn@instructure.com>
Reviewed-by: Kyle Rosenbaum <kyler@instructure.com>
QA-Review: Kyle Rosenbaum <kyler@instructure.com>