Update examples from "ruby:2.5" to "ruby:3.0"

ruby/content.md

@@ -11,7 +11,7 @@ Ruby is a dynamic, reflective, object-oriented, general-purpose, open-source pro
 ## Create a `Dockerfile` in your Ruby app project
 
 ```dockerfile
-FROM %%IMAGE%%:2.5
+FROM %%IMAGE%%:3.0
 
 # throw errors if Gemfile has been modified since Gemfile.lock
 RUN bundle config --global frozen 1
@@ -40,7 +40,7 @@ $ docker run -it --name my-running-script my-ruby-app
 The above example `Dockerfile` expects a `Gemfile.lock` in your app directory. This `docker run` will help you generate one. Run it in the root of your app, next to the `Gemfile`:
 
 ```console
-$ docker run --rm -v "$PWD":/usr/src/app -w /usr/src/app %%IMAGE%%:2.5 bundle install
+$ docker run --rm -v "$PWD":/usr/src/app -w /usr/src/app %%IMAGE%%:3.0 bundle install
 ```
 
 ## Run a single Ruby script
@@ -48,7 +48,7 @@ $ docker run --rm -v "$PWD":/usr/src/app -w /usr/src/app %%IMAGE%%:2.5 bundle in
 For many simple, single file projects, you may find it inconvenient to write a complete `Dockerfile`. In such cases, you can run a Ruby script by using the Ruby Docker image directly:
 
 ```console
-$ docker run -it --rm --name my-running-script -v "$PWD":/usr/src/myapp -w /usr/src/myapp %%IMAGE%%:2.5 ruby your-daemon-or-script.rb
+$ docker run -it --rm --name my-running-script -v "$PWD":/usr/src/myapp -w /usr/src/myapp %%IMAGE%%:3.0 ruby your-daemon-or-script.rb
 ```
 
 ## Encoding