Use Node.js 16 in workflow (which ships with npm 7)

.github/workflows/push.yml

@@ -14,13 +14,10 @@ jobs:
         with:
           fetch-depth: 0
 
-      - name: Setup Node 12
+      - name: Setup Node.js
         uses: actions/setup-node@v2
         with:
-          node-version: 12
-          
-      - name: Setup NPM 7
-        run: npm install -g npm@7
+          node-version: 16
 
       - name: Check cache
         uses: actions/cache@v2