CI: update node versions

Author: azu

.github/workflows/test.yml

@@ -6,7 +6,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        node-version: [ 16, 18 ]
+        node-version: [ 18, 20 ]
     steps:
       - name: checkout
         uses: actions/checkout@v4