actors folder clogs up directory

### Quick summary

It appears that the actors folder in the Wordpress directory is constantly filling up, making for bloated directory.
(wp-content->uploads->activitypub->actors)

Looks like profile pics are stored in here. But they are never cleared. 1000s of profile pics are stored, even if the WP AP account only follows 10 profiles. Whatsmore, some profile pics have new versions uploaded daily with the old versions still stored, leaving multiple copies of the same image. Looking at three sites using the AP plugin two have 35mb worth of data of profile pictures stored here, while the other has over 750mb!

Could there be a way to flush this information so it is not stored eternally?

### Steps to reproduce

Go to wp-content->uploads->activitypub->actors and see how much data is in there.

### Site owner impact

Between 20% and 60% of the total website/platform users

### Severity

Moderate

### What other impact(s) does this issue have?

_No response_

### If a workaround is available, please outline it here.

_No response_

Start by inspecting wp-content/uploads/activitypub/actors and the code responsible for storing profile pictures there. Determine how obsolete images and repeated versions are identified and what cleanup behavior is expected. Done should mean the directory no longer grows indefinitely with unused or superseded profile pictures.

Written by the indexing model from the issue text.