Symbolize keys to fix question banks fixup

refs: LS-1692
flag = none

Test plan:
- Import https://pcraighill.test.instructure.com/courses/221
- View /courses/:course_id/question_banks
- Verify that there are broken questions
- Apply fixup /courses/:course_id/question_banks?fixup_quiz_math_questions=1
- Verify that all questions are fixed

Change-Id: I43ec60fc07ce5f1e4336f1ad64261640ec16f7d1
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/254786
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
Reviewed-by: Jeremy Stanley <jeremy@instructure.com>
QA-Review: Nate Armstrong <narmstrong@instructure.com>
Product-Review: Nate Armstrong <narmstrong@instructure.com>

lib/quiz_math_data_fixup.rb

@@ -29,7 +29,7 @@ module QuizMathDataFixup
     questions.find_each do |quiz_question|
       begin
         old_data = quiz_question.question_data.to_hash
-        new_data = fixup_question_data(quiz_question.question_data.to_hash)
+        new_data = fixup_question_data(quiz_question.question_data.to_hash.symbolize_keys)
         quiz_question.write_attribute(:question_data, new_data) if new_data != old_data
         if quiz_question.changed?
           stat = question_bank ? 'updated_math_qb_question' : 'updated_math_question'
@@ -69,7 +69,7 @@ module QuizMathDataFixup
 
     data[:question_text] = fixup_html(data[:question_text]) if data[:question_text].present?
 
-    data[:answers].each_with_index do |answer, index|
+    data[:answers].map(&:symbolize_keys).each_with_index do |answer, index|
       %i[html comments_html].each do |key|
         # if there's html, the text field is used as the title attribute/tooltip
         # clear it out if we updated the html because it's probably hosed.