Update Ruby version to 3.1.1 in GitHub Actions workflow

Author: mehyaa

.github/workflows/docs.yml

@@ -32,7 +32,7 @@ jobs:
             - name: Setup Ruby
               uses: ruby/setup-ruby@v1
               with:
-                  ruby-version: "3.1"
+                  ruby-version: "3.1.1"
                   bundler-cache: true
                   working-directory: ./docs