Run automated bundle-update with Ruby 4.0.0-preview2

Author: soutaro

.github/workflows/bundle-update.yml

@@ -16,7 +16,7 @@ jobs:
       - name: Set up Ruby
         uses: ruby/setup-ruby@v1
         with:
-          ruby-version: '3.4'
+          ruby-version: '4.0.0-preview2'
 
       - name: Set up git
         run: |