infra: use correct health check

infrastructure/docker-compose.run.yml

@@ -10,7 +10,7 @@ services:
     volumes:
       - opencon-logs:/var/log/opencon
     healthcheck:
-      test: curl --fail http://localhost:8000/openapi.json || exit 1
+      test: curl --fail http://localhost:8000/api/conferences/health || exit 1
       interval: 60s
       retries: 3
       start_period: 5s