chore: test only on Node.js v14 and v16

Author: Björn Brauer

.github/workflows/node-ci.yml

@@ -8,7 +8,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        node-version: [14.x, 15.x]
+        node-version: [14.x, 16.x]
     steps:
     - name: Check out repository
       uses: actions/checkout@v2