firebase.messaging.UnregisteredError
# What this PR does _tldr_; we had a lengthy discussion about this [here](https://raintank-corp.slack.com/archives/C04JCU51NF8/p1701893410542629?thread_ts=1701690117.016909&cid=C04JCU51NF8). `firebase.messaging.UnregisteredError` errors occur because of events outside of our control and retrying will never fix them, therefore we should simply skip retrying in this case. We retry these fairly often ([logs](https://ops.grafana-ops.net/explore?schemaVersion=1&panes=%7B%22iWZ%22:%7B%22datasource%22:%22000000193%22,%22queries%22:%5B%7B%22refId%22:%22A%22,%22expr%22:%22%23%20%7Bcluster%3D~%5C%22prod-%28eu-west-0%7Cus-central-0%29%5C%22,%20namespace%3D%5C%22amixr-prod%5C%22%7D%20%7C%3D%20%5C%22task_name%3Dapps.webhooks.tasks.trigger_webhook.execute_webhook%5C%22%20%7C%3D%20%5C%22retry%5C%22%5Cn%7Bcluster%3D~%5C%22prod-%28eu-west-0%7Cus-central-0%29%5C%22,%20namespace%3D%5C%22amixr-prod%5C%22%7D%20%7C%3D%20%5C%22apps.mobile_app.fcm_relay.fcm_relay_async%5C%22%20%7C%3D%20%5C%22UnregisteredError%5C%22%22,%22queryType%22:%22range%22,%22datasource%22:%7B%22type%22:%22loki%22,%22uid%22:%22000000193%22%7D,%22editorMode%22:%22code%22%7D%5D,%22range%22:%7B%22from%22:%22now-7d%22,%22to%22:%22now%22%7D%7D%7D&orgId=1)) which eats up unnecessary celery worker resources. Related to https://github.com/grafana/oncall-private/issues/1820 ## Checklist - [x] Unit, integration, and e2e (if applicable) tests updated - [x] Documentation added (or `pr:no public docs` PR label added if not required) - [x] `CHANGELOG.md` updated (or `pr:no changelog` PR label added if not required)
