Doc fix in `benchmark_long_document_qa_throughput.py` (#11933)

Signed-off-by: Kuntai Du <kuntai@uchicago.edu>

benchmarks/benchmark_long_document_qa_throughput.py

@@ -2,8 +2,7 @@
 Offline benchmark to test the long document QA throughput.
 
 Example usage:
-    # This command run the vllm with 50GB CPU memory for offloading
-    # The workload samples 8 different prompts with a default input
+    # This workload samples 8 different prompts with a default input
     # length of 20000 tokens, then replicates each prompt 2 times 
     # in random order.
     python benchmark_long_document_qa_throughput.py \