chore: update dockerfile for the rails example (#351)

examples/rails/Dockerfile

@@ -1,12 +1,17 @@
 FROM ruby:3.0 AS builder
 
 # Install nodejs in the ruby image
-RUN curl -sL https://deb.nodesource.com/setup_15.x | bash - && apt-get install -y nodejs
+RUN curl -sL https://deb.nodesource.com/setup_16.x | bash - && apt-get install -y nodejs
 RUN npm install -g yarn
 
 # Gems and packages will be cached in a separate image using a mounted volume.
 ENV BUNDLE_PATH /bundler_cache
 ENV YARN_CACHE_FOLDER /yarn_cache
+ENV BUNDLER_VERSION 2.3.22
+
+# Match the version of Bundler with that specified in Gemfile.lock
+RUN gem update --system \
+    && gem install bundler -v $BUNDLER_VERSION
 
 # Set working directory inside the image home.
 ENV APP_PATH /app