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.
Add BI events for tracking email opt-ins
LMS: fix - visually hiding calculator toggle label
Remove extra prerequisites style and add classes
Refrain from setting email opt-in preference when checkbox is missing
Merge pull request #6133 from edx/renzo/track-email-opt-in

Add BI events for tracking email opt-ins
Add compare-branch option to paver run_quality
Merge pull request #6149 from edx/talbs/fix-lms-calculator-toggle

FIX - LMS: Calculator Toggle Label Display
Merge pull request #6137 from edx/renzo/missing-checkbox-absent-preference

Refrain from setting email opt-in preference when checkbox is missing
Fixed plus sign icon for overall grade range add button.
TNL-890
Merge pull request #6143 from edx/waheed/tnl890-fix-plus-sign-overall-grade-range

Fixed plus sign icon for overall grade range add button.
Merge pull request #6064 from Stanford-Online/kluo/quality-compare-branch-option

Add compare-branch option to paver run_quality
Merge pull request #5842 from Stanford-Online/giulio/prerequisites-style-fixes

Remove extra prerequisites style and class
Merge pull request #6065 from stvstnfrd/debt/xml-cleanup

Remove antiquated cleanup script
Add base support for cohorted group configurations

TNL-649
Add support for user partitioning based on cohort.

JIRA: TNL-710

IMPORTANT: this commit converts the course_groups
package to using migrations.  When deploying to an
existing openedx instance, migration 0001 may fail
with an error indicating that the CourseUserGroup
table already exists.  If this happens, running
the 0001 migration first, with the --fake option,
is recommended.  After performing this step,
remaining migrations should work as expected.
Add group_access field to all xblocks

TNL-670