No longer delete all CourtDates during recalculation

Since we use update_or_create and key off a court's canonical_param we're safe to leave the database populated and run updates. This is probably the right behaviour, as we might want to stash additional court metadata in the database in future.

judgments/management/commands/recalculate_court_dates.py

@@ -19,7 +19,6 @@ def add_arguments(self, parser):
         )
 
     def handle(self, *args, **options):
-        CourtDates.objects.all().delete()
         for court in courts.get_all():
             self.stdout.write(self.style.NOTICE(f"{court.name}"))