Z-index bugs [#3381503]

There are two z-index bugs (see screen recording for both):

The second level active state is showing the grey line overtop of the blue bullet (but is correct on hover).
The first level menu item's hover state z-index is higher than the sticky menu so it floats on top when scrolling.

Comment	File	Size	Author
	Screen Recording 2023-08-16 at 11.52.35 AM.mov	5.6 MB	claireristow

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3381503-z-index-bugs changes, plain diff MR !53
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