Update vllm pin to 12.26 (#5378)

### What this PR does / why we need it?
Update vllm pin to 12.26
### Does this PR introduce _any_ user-facing change?

### How was this patch tested?

- vLLM version: release/v0.13.0
- vLLM main:
81786c8774

---------

Signed-off-by: ZT-AIA <1028681969@qq.com>
Signed-off-by: Mengqing Cao <cmq0113@163.com>
Signed-off-by: ZT-AIA <63220130+ZT-AIA@users.noreply.github.com>
Co-authored-by: Mengqing Cao <cmq0113@163.com>

.github/workflows/pr_test_full.yaml

@@ -74,7 +74,7 @@ jobs:
     name: e2e-full
     strategy:
       matrix:
-        vllm_version: [254f6b986720c92ddf97fbb1a6a6465da8e87e29, v0.13.0]
+        vllm_version: [81786c87748b0177111dfdc07af5351d8389baa1, v0.13.0]
     needs: [changes]
     if: ${{ needs.changes.outputs.e2e_tracker == 'true' }}
     uses: ./.github/workflows/_e2e_test.yaml