Lock rails-new-docker action to Ruby 3.3.1

The 3.3.2 base image doesn't exist yet.

.github/workflows/rails-new-docker.yml

@@ -20,7 +20,7 @@ jobs:
     - name: Set up Ruby 3.3
       uses: ruby/setup-ruby@v1
       with:
-        ruby-version: 3.3
+        ruby-version: 3.3.1
         bundler-cache: true
     - name: Generate --dev app
       run: |