The sort-by UI indicator should be consistent with sorting state in submissions table.

[m-wu]

Steps to reproduce the issue:

1. Go to Submissions table of an assignment
   • Note: the default is sort by Group Name.
2. Sort by Marking State by clicking on the column title
   • Note: the arrow appears besides the column title
3. Click on the Submissions tab to re-open the Submissions table
   • Issue: table is sorted by Group Name as it's the default, but the UI indicator is still on the Marking State column. (See the screenshot below.)