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/design/arch_overview.md

@@ -22,7 +22,7 @@ server.
 
 Here is a sample of `LLM` class usage:
 
-??? Code
+??? code
 
     ```python
     from vllm import LLM, SamplingParams
@@ -180,7 +180,7 @@ vision-language model.
 
     To avoid accidentally passing incorrect arguments, the constructor is now keyword-only. This ensures that the constructor will raise an error if old configurations are passed. vLLM developers have already made this change for all models within vLLM. For out-of-tree registered models, developers need to update their models, for example by adding shim code to adapt the old constructor signature to the new one:
 
-    ??? Code
+    ??? code
 
         ```python
         class MyOldModel(nn.Module):