use new loki syntax

examples/python/docker-compose.oats.yml

@@ -7,6 +7,7 @@ services:
       context: .
       dockerfile: Dockerfile
     environment:
+      OTEL_SERVICE_NAME: "rolldice"
       OTEL_EXPORTER_OTLP_ENDPOINT: http://lgtm:4317
       OTEL_METRIC_EXPORT_INTERVAL: "5000"  # so we don't have to wait 60s for metrics
     ports: