Remove antiquated cleanup script

This script was originally written to clean up XML scripts. In the more
than two years since it was originally written, the only updates it has
received have been to remove PEP8/PyLint/quality violations.

It's hard to imagine that this is still useful to anyone, though I'm
open to discussion.
Merge pull request #6065 from stvstnfrd/debt/xml-cleanup

Remove antiquated cleanup script
WL-164 Unpurchased items are removed when the enrollment period has closed.