Switch to ruby/setup-ruby@v1

Instead of a SHA1, which may be 'safer' but only in theory, unless we really audit each update.

Author: fingolfin

.github/workflows/jekyll.yml

@@ -34,8 +34,7 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v5
       - name: Setup Ruby
-        # https://github.com/ruby/setup-ruby/releases/tag/v1.207.0
-        uses: ruby/setup-ruby@4a9ddd6f338a97768b8006bf671dfbad383215f4
+        uses: ruby/setup-ruby@v1
         with:
           ruby-version: '3.1' # Not needed with a .ruby-version file
           bundler-cache: true # runs 'bundle install' and caches installed gems automatically