clean up

Signed-off-by: Congcong Chen <congcongchen@microsoft.com>

Author: congcongchen123

vllm/attention/layer.py

@@ -160,10 +160,6 @@ def __init__(
         self.attn_type = attn_type
 
         if kv_sharing_target_layer_name is not None:
-            # if not envs.VLLM_USE_V1:
-            #     raise NotImplementedError(
-            #         "Cross-layer KV sharing is not supported in V0.")
-
             validate_kv_sharing_target(
                 prefix,
                 kv_sharing_target_layer_name,