try to escape unmatched brackets in qti question text

test plan:
* import the package referenced in the ticket
* the quiz question titled "soccs7g 9.1-9" should
have a "<" character properly shown in the question text

closes #CNVS-9919

Change-Id: I42af7634f0925d5ffc3acf78c4e139df36ed9e4d
Reviewed-on: https://gerrit.instructure.com/38698
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Jeremy Stanley <jeremy@instructure.com>
QA-Review: Trevor deHaan <tdehaan@instructure.com>
Product-Review: James Williams  <jamesw@instructure.com>