Bump CI node version to 20

Required for the built-in test runner used by `npm test`, which is
only stable on Node >=20.

Author: claude

.github/workflows/ci.yml

@@ -10,7 +10,7 @@ jobs:
 
     - uses: actions/setup-node@v2
       with:
-        node-version: '16'
+        node-version: '20'
 
     - run: npm install
       working-directory: node-drivers