fix: use notEmpty for endpointnames in traces-list expected data

The endpointnames value is non-deterministic — different E2E test
configurations produce different entry endpoints (/artist-consumer
in gRPC tests, /artist-provider in profiling tests). Use notEmpty
check instead of hardcoding either endpoint name.

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

Author: wu-sheng

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

@@ -19,8 +19,11 @@ traces:
   - segmentid: {{ notEmpty .segmentid }}
     endpointnames:
     {{- contains .endpointnames }}
-      - /artist-consumer
+      - {{ notEmpty (index .endpointnames 0) }}
     {{- end }}
+    # Note: endpointnames value is non-deterministic (/artist-consumer or
+    # /artist-provider depending on which segment OAP processes first).
+    # Use notEmpty instead of hardcoding a specific endpoint name.
     duration: {{ ge .duration 0 }}
     start: {{ notEmpty .start}}
     iserror: false