[CI] Fix ut ci: no space on the device (#4662)

### What this PR does / why we need it?
The current ut ci is encountering a disk space shortage issue, see
https://github.com/vllm-project/vllm-ascend/actions/runs/19884417749/job/56990694594?pr=4168

### Does this PR introduce _any_ user-facing change?
N/A

### How was this patch tested?
CI passed with new added/existing test.


- vLLM version: 86e178f7c4d8c3b0eaf3c8e3f810a83f63b90e24
- vLLM main:
86e178f7c4

---------

Signed-off-by: wxsIcey <1790571317@qq.com>

.github/workflows/vllm_ascend_test_pr_light.yaml

@@ -85,7 +85,14 @@ jobs:
     strategy:
       matrix:
         vllm_version: [86e178f7c4d8c3b0eaf3c8e3f810a83f63b90e24]
+        
     steps:
+      - name: Free up disk space
+        uses: jlumbroso/free-disk-space@54081f138730dfa15788a46383842cd2f914a1be # v1.3.1
+        with:
+          tool-cache: true
+          docker-images: false
+
       - name: Install packages
         run: |
           apt-get update -y
@@ -109,6 +116,11 @@ jobs:
 
       - name: Install vllm-project/vllm-ascend
         run: |
+          export TMPDIR=/mnt
+          rm -f /usr/share/dotnet
+          rm -rf /opt/ghc
+          rm -rf "/usr/local/share/boost"
+          rm -rf "$AGENT_TOOLSDIRECTORY"
           export PIP_EXTRA_INDEX_URL=https://mirrors.huaweicloud.com/ascend/repos/pypi
           export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/usr/local/Ascend/ascend-toolkit/latest/x86_64-linux/devlib
           python3 -m pip install -r requirements-dev.txt --extra-index https://download.pytorch.org/whl/cpu/