Clean up Time Machine

While I'm not sure about this, are you sure you even need to do it?

When Time Machine runs out of space, it automatically remove the old versions of files from the backup ensuring you always retail the more up-to-date versions.

No. Time Machine looks after itself and deletes the oldest backups when it needs the space. Whatever you do DO NOT fiddle with or try to manually delete any backups! Assuming your Time Machine disk is dedicated to Time Machine (ie. nothing else on the disk, just one TM partition) and is correctly formatted (Mac OS Extended (Journaled)...TM still doesn't work on APFS formatted drives as far as I know!) then TM looks after itself, there's nothing for you to do! Hope this helps you! Regards, Ian.