[Doc] Update usage of --limit-mm-per-prompt (#34148)

Signed-off-by: DarkLight1337 <tlleungac@connect.ust.hk>

examples/offline_inference/mistral-small.py

@@ -18,11 +18,11 @@ from vllm.assets.image import ImageAsset
 # # Mistral format
 # vllm serve mistralai/Mistral-Small-3.1-24B-Instruct-2503 \
 #   --tokenizer-mode mistral --config-format mistral --load-format mistral \
-#   --limit-mm-per-prompt '{"image":4}' --max-model-len 16384
+#   --limit-mm-per-prompt.image 4 --max-model-len 16384
 #
 # # HF format
 # vllm serve mistralai/Mistral-Small-3.1-24B-Instruct-2503 \
-#   --limit-mm-per-prompt '{"image":4}' --max-model-len 16384
+#   --limit-mm-per-prompt.image 4 --max-model-len 16384
 # ```
 #
 # - Client:

examples/online_serving/openai_chat_completion_client_for_multimodal.py

@@ -10,7 +10,7 @@ vllm serve llava-hf/llava-1.5-7b-hf
 
 (multi-image inference with Phi-3.5-vision-instruct)
 vllm serve microsoft/Phi-3.5-vision-instruct --runner generate \
-    --trust-remote-code --max-model-len 4096 --limit-mm-per-prompt '{"image":2}'
+    --trust-remote-code --max-model-len 4096 --limit-mm-per-prompt.image 2
 
 (audio inference with Ultravox)
 vllm serve fixie-ai/ultravox-v0_5-llama-3_2-1b \

examples/pooling/classify/vision_classification_online.py

@@ -7,7 +7,7 @@ NOTE:
     vllm serve muziyongshixin/Qwen2.5-VL-7B-for-VideoCls \
          --runner pooling \
          --max-model-len 5000 \
-         --limit-mm-per-prompt '{"video": 1}' \
+         --limit-mm-per-prompt.video 1 \
          --hf-overrides '{"text_config": {"architectures": ["Qwen2_5_VLForSequenceClassification"]}}'
 """