CI: use node-version

Author: azu

.github/workflows/test.yml

@@ -8,7 +8,7 @@ jobs:
     runs-on: ubuntu-18.04
     strategy:
       matrix:
-        node_version: [ 12, 14, 16 ]
+        node-version: [ 12, 14, 16 ]
     steps:
       - name: checkout
         uses: actions/checkout@v2