Change comment location (#4432)

### What this PR does / why we need it?
When running 'python example.py',connection issues often occur.The
solution is to comment out the first line the code.
Complete the specific names of machines A2 and A3.
Standardize document format,a space should be added after the colon.
### Does this PR introduce _any_ user-facing change?
no
### How was this patch tested?
ut

- vLLM version: v0.11.2

---------

Signed-off-by: herizhen <you@example.com>
Co-authored-by: herizhen <you@example.com>

docs/source/installation.md

@@ -261,8 +261,14 @@ for output in outputs:
 Then run:
 
 ```bash
-# Try `export VLLM_USE_MODELSCOPE=true` and `pip install modelscope`
-# to speed up download if huggingface is not reachable.
+python example.py
+```
+
+If you encounter a connection error with Hugging Face (e.g., `We couldn't connect to 'https://huggingface.co' to load the files, and couldn't find them in the cached files.`), run the following commands to use ModelScope as an alternative:
+
+```bash
+export VLLM_USE_MODELSCOPE = true
+pip install modelscope
 python example.py
 ```