workflows: Update node-versions of action runners

- Remove v12 and v14
- Add v18 and v20

Author: fordN

.github/workflows/ci.yml

@@ -16,7 +16,7 @@ jobs:
 
     strategy:
       matrix:
-        node-version: [12, 14, 16]
+        node-version: [16, 18, 20]
 
     steps:
     - name: Setup PostgreSQL