🐛 Fix workflow to deploy RDoc to GitHub pages

This was broken by 7017c97.

Author: nevans

.github/workflows/pages.yml

@@ -23,6 +23,7 @@ jobs:
       - name: Setup Ruby
         uses: ruby/setup-ruby@v1
         with:
+          ruby-version: '3.4'
           bundler-cache: true
       - name: Setup Pages
         id: pages