chore: drop node 16

Author: mshima

.github/workflows/ci.yml

@@ -16,7 +16,7 @@ jobs:
       fail-fast: false
       matrix:
         os: [ubuntu-latest, windows-latest, macos-latest]
-        node-version: [16.x, 18.x]
+        node-version: [18.x]
 
     steps:
       - uses: actions/checkout@v3