typing: Amend inaccurate type annotations.

This amend some type annotations that turn out to be inaccurate with
django-stubs.

analytics/views/activity_common.py

@@ -5,7 +5,7 @@ from typing import Any, Dict, List, Optional, Sequence
 
 import pytz
 from django.conf import settings
-from django.db import connection
+from django.db.backends.utils import CursorWrapper
 from django.db.models.query import QuerySet
 from django.template import loader
 from django.urls import reverse
@@ -39,7 +39,7 @@ def make_table(
     return content
 
 
-def dictfetchall(cursor: connection.cursor) -> List[Dict[str, Any]]:
+def dictfetchall(cursor: CursorWrapper) -> List[Dict[str, Any]]:
     "Returns all rows from a cursor as a dict"
     desc = cursor.description
     return [dict(zip((col[0] for col in desc), row)) for row in cursor.fetchall()]