DOCS/interface-changes.rst: simplify playback abort change description

Although it was not true at the time this was written, both the
"program" and "cache-size" are gone now.

Since the changelog is for the entire next release, it makes no sense to
mention these removed properties.

It also happens to make the description of this much simpler, because
it's a non-issue now. It's probably not even worth mentioning anymore.