Update node baseline

.github/workflows/subxt-diff.yml

@@ -16,6 +16,8 @@ jobs:
     steps:
       - name: Checkout
         uses: actions/checkout@v4
+        with:
+          ref: "runtime-${{ github.event.inputs.spec_version }}"
       - name: Local build new Node
         uses: ./.github/workflow-templates/cargo-build
       - name: Upload Node