chore(seer): Unregister unused flag (#91902)

Removing unused `trigger-issue-summary-on-alerts` flag

Author: roaga

src/sentry/features/temporary.py

@@ -531,8 +531,6 @@ def register_temporary_features(manager: FeatureManager):
     manager.add("projects:use-eap-spans-for-metrics-explorer", ProjectFeature, FeatureHandlerStrategy.FLAGPOLE, api_expose=False)
     # Enable tagging span with whether or not we should ingest it in the EAP
     manager.add("projects:ingest-spans-in-eap", ProjectFeature, FeatureHandlerStrategy.FLAGPOLE, api_expose=False)
-    # Enables automatically triggering issue summary on alerts
-    manager.add("projects:trigger-issue-summary-on-alerts", ProjectFeature, FeatureHandlerStrategy.FLAGPOLE, api_expose=False)
     # Enable num events in an issue debugging
     manager.add("projects:num-events-issue-debugging", ProjectFeature, FeatureHandlerStrategy.FLAGPOLE, api_expose=False)