Use the default baggageclaim driver set in the concourse binary

[taylorsilva]

which is detect and will use overlay most likely. naive is really slow once you have large files involved.

Why do we need this PR?

We should use the defaults in the binary instead of setting our own in the chart.

Contributor Checklist

• [x] Variables are documented in the README.md
• [x] Which branch are you merging into?
  • master is for changes related to the current release of the concourse/concourse:latest image and should be good to publish immediately
  • dev is for changes related to the next release of Concourse (aka unpublished code on master in concourse/concourse)

Reviewer Checklist

This section is intended for the core maintainers only, to track review progress. Please do not fill out this section.

• [ ] Code reviewed
• [ ] Topgun tests run
• [ ] Back-port if needed
• [ ] Is the correct branch targeted? (master or dev)