Drop support for node v12.x

Mocha has dropped support for v12.x

See breaking changes for v10.0.0:
https://github.com/mochajs/mocha/blob/main/CHANGELOG.md#1000--2022-05-01

Author: vikiv480

.github/workflows/ci.yml

@@ -11,7 +11,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        node: [12.x, 14.x, 16.x]
+        node: [14.x, 16.x]
 
     steps:
     - name: Checkout code