fix: update node to 20.x in release workflow (openscd#1716)

Author: noraeb

.github/workflows/release-please.yml

@@ -25,7 +25,7 @@ jobs:
         if: ${{ steps.release.outputs.release_created }}
       - uses: actions/setup-node@v4
         with:
-          node-version: 18
+          node-version: "20.x"
           registry-url: "https://registry.npmjs.org"
         if: ${{ steps.release.outputs.release_created }}
       - run: npm ci --include=optional