fix: fix some args desc (#2487)

vllm/prefix.py

@@ -11,7 +11,6 @@ class Prefix:
         prefix caching in the future.
 
     Args:
-        prefix_id: The id of the prefix in the prefix pool.
         token_ids: The token ids of the prefix.
         block_size: The block size of the executed model.
     """

vllm/sequence.py

@@ -229,6 +229,7 @@ class SequenceGroup:
         seqs: The list of sequences.
         sampling_params: The sampling parameters used to generate the outputs.
         arrival_time: The arrival time of the request.
+        prefix: The prefix of the prompt of the sequence group.
     """
 
     def __init__(