Drop v16/v18.

Author: stephenh

.github/workflows/build.yml

@@ -12,7 +12,7 @@ jobs:
 
     strategy:
       matrix:
-        node-version: [16.x, 18.x, 20.x]
+        node-version: [20.x, 21.x]
 
     steps:
       - uses: actions/checkout@v4