Update QA delete_subgroups task to skip marked

Closes #199279 (closed)

Updates the QA delete_subgroups task to now take account for subgroups that are already marked for deletion. This functionality changed recently to be a soft deletion instead of hard and subgroups now stick around for a week to prevent accidental deletions.

Task now loops through and filters out any subgroups already marked for deletion.

bundle exec rake delete_subgroups GITLAB_ADDRESS=$GITLAB_ADDRESS
Running...
Number of Sub Groups not already marked for deletion: 98
Deleting 98 subgroups...
..................................................................................................
Done
Job succeeded