[Security] Drop the hard-coded API key from the DS-V4.1 serving config (#1396)

The Phase 3 YAML shipped a literal api-key. Pass the key at launch instead,
with --api-key or VLLM_API_KEY. The old key is in git history and must be
treated as exposed.

Co-authored-by: yangzhuxinyzx <Susannah_Carterect@gmx.ca>
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

benchmarks/deepseek_v41/serve-ds41-phase3.yaml

@@ -61,4 +61,4 @@ kernel-config:
     embedding_storage: original
     prefill_min_m: 1
     dequant_workspace_bytes: 33554432
-api-key: sk-ds41-dNCMTcG1OUSl
+# Set an API key at launch: --api-key <key> or the VLLM_API_KEY environment variable.