ci: use Node.js 24 for OIDC release

The release job set node-version 20 but installed npm@latest (npm 12),
which requires Node.js >= 22.22.2, so `npm install -g npm@latest` failed
with EBADENGINE. Node 20's bundled npm 10 also doesn't support OIDC
trusted publishing (needs >= 11.5.1).

Bump the release job to Node.js 24 (via setup-node v6) so npm@latest
installs cleanly and supports trusted publishing.

Author: gxkl

.github/workflows/release.yml

@@ -34,9 +34,9 @@ jobs:
           fetch-depth: 0
 
       - name: Setup Node.js
-        uses: actions/setup-node@v4
+        uses: actions/setup-node@v6
         with:
-          node-version: 20
+          node-version: 24
           registry-url: 'https://registry.npmjs.org'
 
       # OIDC trusted publishing requires npm >= 11.5.1