fix: remove hardcoded endpoint name in E2E traces-list expected data

The traces-list.yml expected '/artist-provider' in endpointnames,
but traces can have either '/artist-provider' or '/artist-consumer'
depending on reporting order. Use notEmpty check instead of
hardcoding a specific endpoint name.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: wu-sheng

tests/e2e/case/expected/traces-list.yml

@@ -19,7 +19,7 @@ traces:
   - segmentid: {{ notEmpty .segmentid }}
     endpointnames:
     {{- contains .endpointnames }}
-      - /artist-provider
+      - {{ notEmpty (index .endpointnames 0) }}
     {{- end }}
     duration: {{ ge .duration 0 }}
     start: {{ notEmpty .start}}