maint: Upgrade GitHub Actions node version.

Author: thet

.github/workflows/test.yml

@@ -14,6 +14,6 @@ jobs:
     - uses: actions/checkout@v4
     - uses: actions/setup-node@v4
       with:
-        node-version: '18'
+        node-version: '20'
         cache: 'yarn'
     - run: make check