Update ruby/setup-ruby digest to a4f8389

Author: renovate[bot]

.github/workflows/jekyll-gh-pages.yml

@@ -23,7 +23,7 @@ jobs:
 
       - name: Setup Ruby
         id: setup-ruby
-        uses: ruby/setup-ruby@a4effe49ee8ee5b8b5091268c473a4628afb5651
+        uses: ruby/setup-ruby@a4f838919020b587bb8dd4493e8881bb113d3be7
         with:
           ruby-version: '3.4.2'
           bundler-cache: true