move to currently active node versions for testing only

Author: birm

.github/workflows/node.js.yml

@@ -12,7 +12,7 @@ jobs:
 
     strategy:
       matrix:
-        node-version: [12.x, 14.x, 15.x]
+        node-version: [14.x, 16.x, 18.x]
         # See supported Node.js release schedule at https://nodejs.org/en/about/releases/
 
     steps: