Update UnderlineNav-item to not wrap counter & icon

[jonrohan]

I'm running into the situation where the underline nav items will wrap counter and icon items at certain screen sizes.

I want to add a no wrap rule to each UnderlineNav-item so that the elements don't wrap like this.

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[simurai]

Looks good.

What's the urgency to ship it on dotcom? Maybe we can do another release together with #1028.

[jonrohan]

What's the urgency to ship it on dotcom? Maybe we can do another release together with

It's not super urgent at the moment, I'm using a no-wrap utility. So i'm ok for it to go out with whatever next release is coming up