Use latest ruby/setup-ruby action

Fixes pages not building on ubuntu-latest due to an ancient version of setup-ruby.
Also bumps Ruby version 3.0 -> 3.3.

.github/workflows/jekyll-build.yml

@@ -14,9 +14,9 @@ jobs:
         id: pages
         uses: actions/configure-pages@v2
       - name: Setup Ruby
-        uses: ruby/setup-ruby@0a29871fe2b0200a17a4497bae54fe5df0d973aa # v1.115.3
+        uses: ruby/setup-ruby@v1
         with:
-          ruby-version: '3.0' # Not needed with a .ruby-version file
+          ruby-version: '3.3' # Not needed with a .ruby-version file
           bundler-cache: true # runs 'bundle install' and caches installed gems automatically
           cache-version: 0 # Increment this number if you need to re-download cached gems
       - name: Define additional Jekyll variables