[CI] CI on ubuntu-24.04

Author: amatsuda

.github/workflows/main.yml

@@ -74,7 +74,7 @@ jobs:
           - ruby_version: '3.1'
             rails_version: '8.0'
 
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-24.04
 
     env:
       RAILS_VERSION: ${{ matrix.rails_version }}