test(e2e): add startup delay to phoenix tracing fixture to fix timeouts

Author: visahak

tests/e2e/test_e2e_pipeline.py

@@ -53,6 +53,7 @@ def phoenix_server():
             # specifically hit the status endpoint
             urllib.request.urlopen("http://localhost:6006/status", timeout=2)
             print("Phoenix server is up and running.")
+            time.sleep(5)  # Wait for OTLP receivers to fully spin up
             break
         except Exception:
             # Also check if process crashed early