Whitelist object types in the index query

Select the outbox object types that we want to show on the notes page
instead of removing objects that we don't want to show.
That way, it's easier to ensure that there are no objects messing up the
object count/empty checks.

Partially fixes https://todo.sr.ht/~tsileo/microblog.pub/65

app/main.py

@@ -296,7 +296,7 @@ async def index(
         models.OutboxObject.visibility == ap.VisibilityEnum.PUBLIC,
         models.OutboxObject.is_deleted.is_(False),
         models.OutboxObject.is_hidden_from_homepage.is_(False),
-        models.OutboxObject.ap_type != "Article",
+        models.OutboxObject.ap_type.in_(["Announce", "Note", "Video", "Question"]),
     )
     q = select(models.OutboxObject).where(*where)
     total_count = await db_session.scalar(