Fix task logging error

We're having weird issues with the celery task, and while I'm not sure this is the culprit, it is the only error I'm seeing in the logs at the moment.

uber/tasks/mivs.py

@@ -31,9 +31,7 @@ def mivs_assign_game_codes_to_judges():
                             break
                     else:
                         log.warning(
-                            'Unable to find free code for game {} to assign to judge {}',
-                            game.title,
-                            review.judge.full_name)
+                            f'Unable to find free code for game {game.title} to assign to judge {review.judge.full_name}')
 
 
 def should_send_reminder(session, studio, keys, ident_prepend):