[Doc] Remove outdated comment to avoid misunderstanding (#9287)

vllm/core/block_manager_v2.py

@@ -24,9 +24,8 @@ class BlockSpaceManagerV2(BlockSpaceManager):
     autoregressively-generated tokens, and other advanced features such as
     prefix caching, forking/copy-on-write, and sliding-window memory allocation.
 
-    The current implementation is partial; in particular prefix caching and
-    sliding-window are not feature complete. This class implements the design
-    described in https://github.com/vllm-project/vllm/pull/3492.
+    This class implements the design described in
+    https://github.com/vllm-project/vllm/pull/3492.
 
     Lookahead slots
         The block manager has the notion of a "lookahead slot". These are slots