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/configuration/conserving_memory.md

@@ -57,7 +57,7 @@ By default, we optimize model inference using CUDA graphs which take up extra me
 
 You can adjust `compilation_config` to achieve a better balance between inference speed and memory usage:
 
-??? Code
+??? code
 
     ```python
     from vllm import LLM
@@ -129,7 +129,7 @@ reduce the size of the processed multi-modal inputs, which in turn saves memory.
 
 Here are some examples:
 
-??? Code
+??? code
 
     ```python
     from vllm import LLM