Updates to account for recent CSS changes in platform. Changes made include:
- Removing h3 element response__submission__status__title, this is more properly just a div
- Removing style %t-subheading, as %t-titlecase breaks a11y so %t-heading may be used everywhere
- Adding staff-assessment__display__header and staff__grade__title to _shame.css
- Modifying acceptance tests to account for loss of %t-titlecase
