Use a prebuilt image to avoid installing ruby

Missing dependencies caused the cleanup job to fail.

Instead of updating dependencies whenever they change we can use the image we use to run QA tests, which should have all the dependencies we'll need.

This means we don't have to install ruby or bundler because they're already in the image.

We also don't need the libxml packages. I think they were included in a different job this one was copied from. The rake task runs without those packages