Update node version and os in pipeline

Author: devrnt

.github/workflows/main.yml

@@ -7,8 +7,8 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        node: ['12.x', '14.x']
-        os: [ubuntu-latest]
+        node: ['14.x', '16.x']
+        os: [ubuntu-20.04]
 
     steps:
       - name: Checkout repo