Enable v2 by default

Signed-off-by: yizhang-nv <187001205+yizhang-nv@users.noreply.github.com>

Author: yizhang-nv

tensorrt_llm/llmapi/llm_args.py

@@ -1763,7 +1763,7 @@ class KvCacheConfig(StrictBaseModel, PybindMirror):
                                   description="The number of tokens per block.")
 
     use_kv_cache_manager_v2: bool = Field(
-        default=False,
+        default=True,
         status="prototype",
         description="Whether to use the KV cache manager v2 (experimental).")