fix(ci): Align Ruby version in workflow with .ruby-version

Author: bits-bytes-nn

.github/workflows/jekyll.yml

@@ -23,7 +23,7 @@ jobs:
       - name: Setup Ruby
         uses: ruby/setup-ruby@v1
         with:
-          ruby-version: '3.1'
+          ruby-version: '2.6.3'
           bundler-cache: true
           cache-version: 0
       - name: Setup Pages