chore(aci milestone 3): use flagpole (#89396)

Set `MetricAlertFire.use_flagpole_for_all_features = True`

Author: mifu67

src/sentry/incidents/grouptype.py

@@ -72,6 +72,7 @@ def get_group_key_values(
 # like these when we're sending issues as alerts
 @dataclass(frozen=True)
 class MetricAlertFire(GroupType):
+    use_flagpole_for_all_features = True
     type_id = 8001
     slug = "metric_alert_fire"
     description = "Metric alert fired"