♻️(backend) do not paginate threads list response

The threads list action was paginated its response. this is not the
behavior we want. all threads should be loaded when the document is
loaded.

src/backend/core/api/viewsets.py

@@ -2757,7 +2757,7 @@ class ThreadViewSet(
     """Thread API: list/create threads and nested comment operations."""
 
     permission_classes = [permissions.CommentPermission]
-    pagination_class = Pagination
+    pagination_class = None
     serializer_class = serializers.ThreadSerializer
     queryset = models.Thread.objects.select_related("creator", "document").filter(
         resolved=False