run CI against node 16, drop 12

Author: tdumitrescu

.github/workflows/tests.yml

@@ -13,7 +13,7 @@ jobs:
 
     strategy:
       matrix:
-        node-version: [12.x, 14.x]
+        node-version: [14.x, 16.x]
 
     steps:
     - uses: actions/checkout@v2