ci: bump release Node to 24 so npm@latest installs

npm@latest now resolves to npm@12, which dropped Node 20 support
(requires ^22.22.2 || ^24.15.0 || >=26.0.0). The release job pinned
Node 20, so `npm install -g npm@latest` failed with EBADENGINE and
skipped GoReleaser. Node 24 is already the actions runtime and ships
npm >= 11.5.1 for OIDC trusted publishing.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: hiroTamada

.github/workflows/release.yaml

@@ -35,7 +35,7 @@ jobs:
       - name: Set up Node.js
         uses: actions/setup-node@v6
         with:
-          node-version: '20'
+          node-version: '24'
           registry-url: 'https://registry.npmjs.org'
 
       - name: Ensure latest npm (>= 11.5.1 for OIDC)