Ignore Celery task results

Since we don't use the results of our Celery tasks (all of them return
None implicitly), it's prudent to set the ignore_result flag, for a
potential performance improvement. See the Celery docs for details [1].

We could do this with the global CELERY_IGNORE_RESULT setting, but it
offers more flexibility if we want to use task results in the future to
set it on a per-task basis.

[1]: https://docs.celeryq.dev/en/stable/userguide/tasks.html#ignore-results-you-don-t-want

bookwyrm/activitypub/base_activity.py

@@ -241,7 +241,7 @@ class ActivityObject:
         return data
 
 
-@app.task(queue=MEDIUM)
+@app.task(queue=MEDIUM, ignore_result=True)
 @transaction.atomic
 def set_related_field(
     model_name, origin_model_name, related_field_name, related_remote_id, data