[main][Docs] Fix spelling errors across documentation (#6649)

Fix various spelling mistakes in the project documentation to improve
clarity and correctness.
- vLLM version: v0.15.0
- vLLM main:
d7e17aaacd

---------

Signed-off-by: SlightwindSec <slightwindsec@gmail.com>

docs/source/tutorials/Qwen-VL-Dense.md

@@ -548,7 +548,7 @@ lm_eval \
 
 Refer to [vllm benchmark](https://docs.vllm.ai/en/latest/contributing/benchmarks.html) for more details.
 
-There are three `vllm bench` subcommand:
+There are three `vllm bench` subcommands:
 
 - `latency`: Benchmark the latency of a single batch of requests.
 - `serve`: Benchmark the online serving throughput.