[Misc] Clean up HIDDEN_DEPRECATED_METRICS after metric removal (#33323)

Signed-off-by: carlory <baofa.fan@daocloud.io>
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

tests/entrypoints/instrumentator/test_metrics.py

@@ -231,11 +231,7 @@ EXPECTED_METRICS_MM = [
     "vllm:mm_cache_hits",
 ]
 
-HIDDEN_DEPRECATED_METRICS: list[str] = [
-    "vllm:gpu_cache_usage_perc",
-    "vllm:gpu_prefix_cache_queries",
-    "vllm:gpu_prefix_cache_hits",
-]
+HIDDEN_DEPRECATED_METRICS: list[str] = []
 
 
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