ImageProxy has been removed. On upgrade, there is an option to restore the original remote image links, or direct links to the cached image which will be retained.

почему они это сделали?

Цитата

The primary reason was both compatibility and a security report we received.

Also, it was introduced years ago to handle images that were not on HTTPS to proxy them thereby allowing your own site to remain 100% secure. But, technology changes and today it's very rare to come across any site not on a secure connection.

So it was removed since it's really not needed any longer as technology has progressed and because it introduced a possible security issue.

Уже небезопасных сайтов осталось очень мало.