Make distinct code and console admonitions so readers are less likely to miss them (#20585)

Signed-off-by: Harry Mellor <19981378+hmellor@users.noreply.github.com>

docs/serving/integrations/langchain.md

@@ -13,7 +13,7 @@ pip install langchain langchain_community -q
 
 To run inference on a single or multiple GPUs, use `VLLM` class from `langchain`.
 
-??? Code
+??? code
 
     ```python
     from langchain_community.llms import VLLM