Move send_alert_group_signal to critical (#5168)

# What this PR does

## Which issue(s) this PR closes

Related to [issue link here]

<!--
*Note*: If you want the issue to be auto-closed once the PR is merged,
change "Related to" to "Closes" in the line above.
If you have more than one GitHub issue that this PR closes, be sure to
preface
each issue link with a [closing
keyword](https://docs.github.com/en/get-started/writing-on-github/working-with-advanced-formatting/using-keywords-in-issues-and-pull-requests#linking-a-pull-request-to-an-issue).
This ensures that the issue(s) are auto-closed once the PR has been
merged.
-->

## Checklist

- [ ] Unit, integration, and e2e (if applicable) tests updated
- [ ] Documentation added (or `pr:no public docs` PR label added if not
required)
- [ ] Added the relevant release notes label (see labels prefixed w/
`release:`). These labels dictate how your PR will
    show up in the autogenerated release notes.

engine/settings/celery_task_routes.py

@@ -7,7 +7,6 @@ CELERY_TASK_ROUTES = {
     "apps.alerts.tasks.delete_alert_group.send_alert_group_signal_for_delete": {"queue": "default"},
     "apps.alerts.tasks.delete_alert_group.finish_delete_alert_group": {"queue": "default"},
     "apps.alerts.tasks.invalidate_web_cache_for_alert_group.invalidate_web_cache_for_alert_group": {"queue": "default"},
-    "apps.alerts.tasks.send_alert_group_signal.send_alert_group_signal": {"queue": "default"},
     "apps.alerts.tasks.wipe.wipe": {"queue": "default"},
     "common.oncall_gateway.tasks.create_oncall_connector_async": {"queue": "default"},
     "common.oncall_gateway.tasks.delete_oncall_connector_async": {"queue": "default"},
@@ -134,6 +133,7 @@ CELERY_TASK_ROUTES = {
     "apps.phone_notifications.phone_backend.notify_by_sms_bundle_async_task": {"queue": "critical"},
     "apps.schedules.tasks.drop_cached_ical.drop_cached_ical_for_custom_events_for_organization": {"queue": "critical"},
     "apps.schedules.tasks.drop_cached_ical.drop_cached_ical_task": {"queue": "critical"},
+    "apps.alerts.tasks.send_alert_group_signal.send_alert_group_signal": {"queue": "critical"},
     # GRAFANA
     "apps.grafana_plugin.tasks.sync.plugin_sync_organization_async": {"queue": "grafana"},
     # LONG