ci: remove node 18, add node 24

Author: hi-ogawa

.github/workflows/ci.yml

@@ -29,7 +29,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest]
-        node_version: [18, 20, 22]
+        node_version: [20, 22, 24]
         include:
           # Active LTS + other OS
           - os: macos-latest