Upgrade the version of ruby used in CI (#852)

Author: tylerjw

.github/workflows/deploy.yml

@@ -32,7 +32,7 @@ jobs:
 
     - uses: ruby/setup-ruby@v1
       with:
-        ruby-version: '2.7'
+        ruby-version: '3'
 
     - name: Run htmlproofer.sh
       shell: bash