[stacked] Remove unused directory (#34)

* Add Heroku-24 and ARM support

- Rewrites the project to use a pre-built JRuby binary. Links to downloads are at https://www.jruby.org/download.
- Adds the heroku-24 base image as a build target
- Re-uses the ARM url format for S3 that was introduced in heroku/docker-heroku-ruby-builder#38. Both the Ruby classic buildpack and CNB are tightly coupled to this format and will attempt to download binaries from S3 with cpu architecture information on heroku-24. Once built and uploaded to S3 there should be no changes needed to the buildpack to acquire support for heroku-24 and ARM due to:
  - heroku/heroku-buildpack-ruby#1439
  - heroku/buildpacks-ruby#284

* Remove unused directory

Prior to #33 a script was generated for every Ruby version on every stack to execute docker. This is no longer needed, we can get rid of this directory.

README.md

@@ -11,14 +11,17 @@ See https://github.com/heroku/docker-heroku-ruby-builder#building-with-github-ac
 Make sure you've generated a docker image:
 
 ```
-bundle exec rake "generate_image[heroku-22]"
+bin/activate_docker heroku-24
 ```
 
 Then run the following:
 
 ```
-bundle exec rake "new[9.3.0.0,heroku-22]" &&
-bash rubies/heroku-22/jruby-9.3.0.0.sh &&
-bundle exec rake "upload[9.3.0.0,heroku-22]" &&
-echo "Done building jruby 9.3.0.0 for heroku-22"
+bin/build_jruby heroku-24 9.4.7.0
+```
+
+This will generate tar files in the `builds` folder. You can exercise them by running:
+
+```
+bin/print_summary heroku-24 9.4.7.0
 ```