spec: use hex html escape in rails 2 like rails 3

Change-Id: I258cba55d55eda0c5c35654b2163fb6417fed16f
Reviewed-on: https://gerrit.instructure.com/29609
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Derek DeVries <ddevries@instructure.com>
Product-Review: Ryan Florence <ryanf@instructure.com>
QA-Review: Ryan Florence <ryanf@instructure.com>