`AvatarStack`: `disableExpand` does not disable animation when `Avatar` components within are changed

[gr2m]

Description

follow up to https://github.com/github/github/pull/286539#discussion_r1309192548

Steps to reproduce

263312599-cf8f26f5-ce02-42cf-bf55-9eab78cca6f5.mov

Version

v35.28.0

Browser

No response

[mperrotti]

If this comes up in any planning sessions, you can assign me.