Fix docstring mistake

Signed-off-by: maxDavid40 <maxdavid40@gmail.com>

Author: maxDavid40

vllm/sampling_params.py

@@ -149,7 +149,7 @@ class SamplingParams(
             always return the log probability of the sampled token, so there
             may be up to `logprobs+1` elements in the response.
         prompt_logprobs: Number of log probabilities to return per prompt token.
-        detokenize: Whether to detokenize the output. Defaults to None.
+        detokenize: Whether to detokenize the output. Defaults to True.
         skip_special_tokens: Whether to skip special tokens in the output.
         spaces_between_special_tokens: Whether to add spaces between special
             tokens in the output.  Defaults to True.