ci: update node versions

Author: yyx990803

.github/workflows/test.yml

@@ -7,7 +7,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        node-version: [14, 15]
+        node-version: [14, 16]
     steps:
       - uses: actions/checkout@v1
       - name: Use Node.js ${{ matrix.node-version }}