fix: pass save() arguments by keyword for Django 6.0 compatibility

Django 6.0 will require save()'s force_insert, force_update, using,
and update_fields to be passed as keyword arguments only (positional
support deprecated in 5.1). Updates CourseMode.save() to pass them
by keyword when delegating to super().

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: feanil

common/djangoapps/course_modes/models.py

@@ -268,7 +268,7 @@ def save(self, force_insert=False, force_update=False, using=None):  # pylint: d
         if self.id is None:
             # If this model has no primary key at save time, it needs to be force-inserted.
             force_insert = True
-        super().save(force_insert, force_update, using)
+        super().save(force_insert=force_insert, force_update=force_update, using=using)
 
     @property
     def slug(self):