We have found that users were getting confued by the buttons named
"check," and on their last allowed attempt, "final check."  Check looks
implies something for the user only, not a real problem submission.

So this changes the wording to "Submit" for most attempts, and "Final
Submit" for the last attempt allowed.

We (Stanford) had made a prior change to only say "Submit" on the final
attempt, but condisering that now that seems even more confusing.