[CI] Use offline mode for nightly test (#5187)

### What this PR does / why we need it?
For single node test, the lack of a retry mechanism for accessing
ModelScope resulted in an HTTP 400 error sometimes. I recommend using a
local offline cache instead.

- vLLM version: v0.12.0
- vLLM main:
ad32e3e19c
---------
Signed-off-by: wangli <wangli858794774@gmail.com>

.github/workflows/_e2e_nightly_single_node.yaml

@@ -57,6 +57,9 @@ jobs:
     timeout-minutes: 600
     container:
       image: ${{ inputs.image }}
+    env:
+      TRANSFORMERS_OFFLINE: 1
+      VLLM_USE_MODELSCOPE: True
     steps:
       - name: Check npu and CANN info
         run: |