ci: increase stage-b-test-small-1-gpu partitions from 4 to 5 (#16250)

.github/workflows/pr-test.yml

@@ -516,7 +516,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        partition: [0, 1, 2, 3]
+        partition: [0, 1, 2, 3, 4]
     steps:
       - name: Checkout code
         uses: actions/checkout@v4
@@ -543,7 +543,7 @@ jobs:
           if [[ "${{ needs.check-changes.outputs.continue_on_error }}" == "true" ]]; then
             CONTINUE_ON_ERROR_FLAG="--continue-on-error"
           fi
-          python3 run_suite.py --hw cuda --suite stage-b-test-small-1-gpu --auto-partition-id ${{ matrix.partition }} --auto-partition-size 4 $CONTINUE_ON_ERROR_FLAG
+          python3 run_suite.py --hw cuda --suite stage-b-test-small-1-gpu --auto-partition-id ${{ matrix.partition }} --auto-partition-size 5 $CONTINUE_ON_ERROR_FLAG
 
   stage-b-test-large-1-gpu:
     needs: [check-changes, call-gate, stage-a-test-1, sgl-kernel-build-wheels]