ci: Update deprecated Node 20 on GHA runners (#515)

Updates workflows to use Node 24 as Node 20 is [being
deprecated](https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/).

.github/workflows/reusable-build.yml

@@ -290,9 +290,9 @@ jobs:
           mv ./target/wasm32-unknown-emscripten/release/resolc_web.js ./resolc-wasm32-unknown-emscripten/
 
       - name: Set Up Node.js
-        uses: actions/setup-node@v3
+        uses: actions/setup-node@v6
         with:
-          node-version: "20"
+          node-version: "24"
 
       - name: Basic Sanity Check
         run: |