Filter initial user set by user id for deviations

Fixes #1238. `UsersSearchSelectField` searches by user id, so the
submitters must be a list of user ids instead of profile ids as one
might expect.

deviations/forms.py

@@ -55,7 +55,7 @@ def __init__(self, *args: Any, initial: Optional[Dict[str, Any]] = None, **kwarg
             try:
                 # Support setting the initial value for submitter
                 self.fields['submitter'].initial_queryset = (
-                    course_instance.get_student_profiles().filter(id__in=initial.get('submitter'))
+                    course_instance.get_student_profiles().filter(user_id__in=initial.get('submitter'))
                 )
             except (ValueError, TypeError):
                 pass