remove node 12, 15 from CI

Author: mtrezza

.github/workflows/ci.yml

@@ -24,12 +24,8 @@ jobs:
     strategy:
       matrix:
         include:
-          - name: Node 12
-            NODE_VERSION: 12.22.11
           - name: Node 14
             NODE_VERSION: 14.21.1
-          - name: Node 15
-            NODE_VERSION: 15.14.0
           - name: Node 16
             NODE_VERSION: 16.18.1
           - name: Node 18