Styling adjustment on header for certain pages (Fixes #15873)

[lbrooks81]

If this changeset needs to go into the FXC codebase, please add the WMO and FXC label.

One-line summary

Added styling to fix brief flash of color upon hovering over navigation items

Significant changes and points to review

Issue / Bugzilla link

#15873

Testing

http://localhost:8000/fr/firefox/challenge-the-default/
http://localhost:8000/en/firefox/family/

[janbrasna]

Just quickly looking at the impact: (not diving into formatting and linting as this would fail the checks, starting with important not being allowed generally etc.…)

1. It's not always black, current item uses dark green so there are perhaps more combinations to check for.
2. I might have missed the idea why this is only applied in the js enhanced block, and not universally?
3. There are existing specificity overrides, so this might be worth exploring if such nesting helps with the order:

bedrock/media/css/m24/components/navigation-refresh.scss

Lines 368 to 373 in b57052f

	// extra specificity to override link colors on some Firefox pages
	&:link,
	&:visited {
	color: $color-black;
	text-decoration: none;
	}

[wen-2018]

Closed in favor of #16147

[janbrasna]

@lbrooks81 Thanks for the changeset, it helped tracking down the actual missing anchor in the specificity — but eventually needed a slightly different approach to fit in — but thanks to this contribution things started moving to getting it fixed, so the effort put into the PR is appreciated. 🎩 Thanks again!