Regression: autosave is active when viewing assessment feedback

When viewing assessment feedback as a student, autosave is active.

By itself, this would be mostly harmless, but in one case a student had assessment feedback open in one tab and took another assessment in another tab, and the feedback autosave caused the real assessment responses to be discarded.

Autosave for feedback was disabled in SAM-928 but put back (possibly inadvertently) in SAM-1352.