[Doc] Convert docs to use colon fences (#12471)

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

docs/source/models/extensions/index.md

@@ -1,8 +1,8 @@
 # Built-in Extensions
 
-```{toctree}
+:::{toctree}
 :maxdepth: 1
 
 runai_model_streamer
 tensorizer
-```
+:::

docs/source/models/extensions/runai_model_streamer.md

@@ -48,6 +48,6 @@ You can read further about CPU buffer memory limiting [here](https://github.com/
 vllm serve /home/meta-llama/Llama-3.2-3B-Instruct --load-format runai_streamer --model-loader-extra-config '{"memory_limit":5368709120}'
 ```
 
-```{note}
+:::{note}
 For further instructions about tunable parameters and additional parameters configurable through environment variables, read the [Environment Variables Documentation](https://github.com/run-ai/runai-model-streamer/blob/master/docs/src/env-vars.md).
-```
+:::

docs/source/models/extensions/tensorizer.md

@@ -11,6 +11,6 @@ For more information on CoreWeave's Tensorizer, please refer to
 [CoreWeave's Tensorizer documentation](https://github.com/coreweave/tensorizer). For more information on serializing a vLLM model, as well a general usage guide to using Tensorizer with vLLM, see
 the [vLLM example script](https://docs.vllm.ai/en/stable/getting_started/examples/offline_inference/tensorize_vllm_model.html).
 
-```{note}
+:::{note}
 Note that to use this feature you will need to install `tensorizer` by running `pip install vllm[tensorizer]`.
-```
+:::