Bump actions/checkout from 4 to 6 (#4380)

Bumps [actions/checkout](https://github.com/actions/checkout) from 4 to 6.

- vLLM main:
2918c1b49c

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/workflows/_e2e_nightly_single_node_models.yaml

@@ -78,7 +78,7 @@ jobs:
           git config --global url."https://gh-proxy.test.osinfra.cn/https://github.com/".insteadOf https://github.com/
 
       - name: Checkout vllm-project/vllm-ascend repo
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       - name: Install system dependencies
         run: |
@@ -86,7 +86,7 @@ jobs:
           apt-get -y install gcc g++ cmake libnuma-dev
 
       - name: Checkout vllm-project/vllm repo
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           repository: vllm-project/vllm
           ref: ${{ inputs.vllm }}
@@ -132,7 +132,7 @@ jobs:
           echo "GHA_VLLM_ASCEND_VERSION=$RESOLVED_VERSION" >> $GITHUB_ENV
 
       - name: Checkout vllm-project/vllm-ascend repo
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           repository: vllm-project/vllm-ascend
           path: ./vllm-ascend