fix(collapsible-panel): remove z-index

[montezume]

Summary

Currently when you have a above a CollapsiblePanel, the menu list is hidden by the CollapsiblePanel due to z-index setting. I don't believe we need to set a z-index here.

[tdeekens]

Is this a fix or a breaking change?

[montezume]

IMO it's a fix. We are changing internal styles of the CollapsiblePanel header.

[tdeekens]

Changing styles can be seen as a breaking change of a component library. It's due to the API contract defined. A component/style guide doesn't only have a breaking change when code and usage changes but potentially also when visuals change. Just a thought.

[montezume]

@jonnybel any thoughts ?

[jonnybel]

Well, it does constitute a breaking change, although it might not affect anything, it's hard to tell without seeing how it's being used all over our apps 🤔

But in doubt, it should be considered breaking. Perhaps we can add it to 10.0.0

[montezume]

Well, it sets the z-index of a header container. I can't see how it could effect anything unless there was a CollapsiblePanel with some element inside that overlapped it's header container. I guess we can put it in 10.0.0, since nobody but me noticed the bug in the MC...

[tdeekens]

We can release it as a normal fix. Sorry for making the buzz. It was more about raising awareness for how verionsing can be different on a ui library than this being an apt case for following it.