[CI]: Fix doctest ci for main release (#3451)

### What this PR does / why we need it?
Fix dockets CI for main release.
### Does this PR introduce _any_ user-facing change?
No.
### How was this patch tested?

- vLLM version: v0.11.0rc3
- vLLM main: https://github.com/vllm-project/vllm/commit/v0.11.0

Signed-off-by: menogrey <1299267905@qq.com>

docs/source/installation.md

@@ -141,8 +141,12 @@ Then you can install `vllm` and `vllm-ascend` from **pre-built wheel**:
 ```{code-block} bash
    :substitutions:
 
-# Install vllm-project/vllm from pypi
-pip install vllm==|pip_vllm_version|
+# Install vllm-project/vllm. The newest supported version is |vllm_version|.
+# Because the version |vllm_version| has not been archived in pypi, so you need to install from source.
+git clone --depth 1 --branch |vllm_version| https://github.com/vllm-project/vllm
+cd vllm
+VLLM_TARGET_DEVICE=empty pip install -v -e .
+cd ..
 
 # Install vllm-project/vllm-ascend from pypi.
 pip install vllm-ascend==|pip_vllm_ascend_version|