chore(severity): Remove `projects:first-event-severity-alerting` flag (#71759)

src/sentry/conf/server.py

@@ -1994,8 +1994,6 @@ SENTRY_FEATURES: dict[str, bool | None] = {
     "projects:data-forwarding": True,
     # Enable functionality to discard groups.
     "projects:discard-groups": False,
-    # Enable considering group severity when creating and evaluating alert rules
-    "projects:first-event-severity-alerting": False,
     # Enable calculating a severity score for events which create a new group
     "projects:first-event-severity-calculation": False,
     # Enable escalation detection for new issues

src/sentry/features/temporary.py

@@ -277,7 +277,6 @@ def register_temporary_features(manager: FeatureManager):
     manager.add("projects:ai-autofix", ProjectFeature, FeatureHandlerStrategy.INTERNAL)
     manager.add("projects:alert-filters", ProjectFeature, FeatureHandlerStrategy.INTERNAL)
     manager.add("projects:discard-transaction", ProjectFeature, FeatureHandlerStrategy.INTERNAL)
-    manager.add("projects:first-event-severity-alerting", ProjectFeature, FeatureHandlerStrategy.INTERNAL)
     manager.add("projects:first-event-severity-calculation", ProjectFeature, FeatureHandlerStrategy.INTERNAL)
     manager.add("projects:first-event-severity-new-escalation", ProjectFeature, FeatureHandlerStrategy.INTERNAL)
     manager.add("projects:high-priority-alerts", ProjectFeature, FeatureHandlerStrategy.INTERNAL)