fix(accordion): resolve accordion header z-index issue

[tw15egan]

Closes #5272

Refs #1674

Changes z-index value so that radio buttons are not overlayed on tooltip inside the accordion header.

Changelog

Changed

• Bumped z-index from 0 to 1

Testing / Reviewing

See https://codesandbox.io/s/zen-hofstadter-km7to for example of the issue. Check a radio button, then hover over the filter icon. Inspect .bx--accordion__title and set z-index: 1;, and see that you can no longer see the filled radio button.

[tw15egan]

cc @asudoh , ref'd the PR that added that z-index in case I am missing why it was added in the first place.

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[asudoh]

Thanks @tw15egan - As I think you saw, blame history points to #1671 - Would you be able to double-check if every bullets in there has no problem?

[tw15egan]

@asudoh checked the list and all still seems good 👍

[asudoh]

LGTM 👍 ✅ - Thanks @tw15egan!

[abbeyhrt]

I noticed that the issue is also resolved if the z-index is removed, would that be another way to go about this?

[tw15egan]

@abbeyhrt I think then the accordion header text is covered on hover

[abbeyhrt]

@tw15egan ah that makes sense! Thanks!

[tw15egan]

@abbeyhrt Yeah I think it has to do with the use of before elements to cover up the borders when they are hovered 🤷‍♂