Update actions/setup-node action to v6

Author: renovate[bot]

.github/workflows/checks.yml

@@ -17,7 +17,7 @@ jobs:
     steps:
       - uses: actions/checkout@v4
       - name: Specifically use node LTS.
-        uses: actions/setup-node@v4
+        uses: actions/setup-node@v6
         with:
           node-version: "18"
       - run: npm install

.github/workflows/release-package.yml

@@ -16,7 +16,7 @@ jobs:
       contents: read
     steps:
       - uses: actions/checkout@v4
-      - uses: actions/setup-node@v4
+      - uses: actions/setup-node@v6
         with:
           node-version: 18
           registry-url: https://registry.npmjs.org