Chromatic Menu matrix test has unexpected Firefox diff

[m-akinc]

🧹 Tech Debt

After the recent Chromatic Capture Cloud update, the Menu matrix test has been showing unexpected gaps between some menus and their submenus:
https://www.chromatic.com/test?appId=60e89457a987cf003efc0a5b&id=65d7e05b8ca63d78ed7c6906

I cannot reproduce this in my local Firefox (version 123, as opposed to Chromatic's version 121).
Notably, the menus at the top of each theme section do not have the problem. This feels vaguely similar to the issues we had with the Tooltip matrix story.

[jattasNI]

I saw this again in this build. It does not reproduce for me in macOS Firefox in the corresponding Storybook.

[jattasNI]

Another instance

[jattasNI]

The steps to work around this diff are captured in this comment