[Doc] fix the nit in docs (#6826)

Refresh the doc, fix the nit in the docs

- vLLM version: v0.15.0
- vLLM main:
83b47f67b1

Signed-off-by: wangxiyuan <wangxiyuan1007@gmail.com>

docs/source/installation.md

@@ -164,7 +164,7 @@ VLLM_TARGET_DEVICE=empty pip install -v -e .
 cd ..
 
 # Install vLLM Ascend.
-git clone  --depth 1 --branch |vllm_ascend_version| https://github.com/vllm-project/vllm-ascend.git
+git clone --depth 1 --branch |vllm_ascend_version| https://github.com/vllm-project/vllm-ascend.git
 cd vllm-ascend
 git submodule update --init --recursive
 pip install -v -e .