[Docs] Fix syntax highlighting of shell commands (#19870)

Signed-off-by: Lukas Geiger <lukas.geiger94@gmail.com>

docs/deployment/frameworks/haystack.md

@@ -13,7 +13,7 @@ It allows you to deploy a large language model (LLM) server with vLLM as the bac
 
 - Setup vLLM and Haystack environment
 
-```console
+```bash
 pip install vllm haystack-ai
 ```
 
@@ -21,7 +21,7 @@ pip install vllm haystack-ai
 
 - Start the vLLM server with the supported chat completion model, e.g.
 
-```console
+```bash
 vllm serve mistralai/Mistral-7B-Instruct-v0.1
 ```