typing: Use django-stubs' type annotations for QuerySet.
typing: Use django-stubs' type annotations for QuerySet.

We no longer need to annotate the type of objects returned
from queries since django-stubs plugin infers that already.

Signed-off-by: Zixuan James Li <74923aee05c23ca90566381b5d6b0cd9451b6054@gmail.com>

zulip/zulip,zulip/zulip,zulip/zulip,zulip/zulip,zulip/zulip,zulip/zulip,zulip/zulip