feat(link): update color to foreground-primary

[LuLaValva]

• Fixes Links: Update color #1904

• This PR contains CSS changes
• This PR does not contain CSS changes

Description

• Updated color to match design system

Notes

• There is no specification for :visited links in the design system, so this PR retains the purple color for now.
• Designs include a "standalone link," which may warrant the creation of a new class such as a.link--standalone. However, nav-link already matches the standalone designs so this addition may not be necessary.

Checklist

• I verify the build is in a non-broken state
• I verify all changes are within scope of the linked issue

• I regenerated all CSS files under dist folder
• I tested the UI in all supported browsers
• I did a visual regression check of the components impacted by doing a Percy build and approved the build
• I tested the UI in dark mode and RTL mode
• I added/updated/removed Storybook coverage as appropriate

[agliga]

PR looks good
One more change might be needed. When I open skin site, the menu looks like this:

https://github.com/eBay/skin/blob/master/docs/src/less/breakpoints.less#L44-L46
We should probably set this to primary too

[LuLaValva]

Thanks Andrew, didn't catch that on my end. Should be fixed now.

[ArtBlue]

The PR looks good, but there is a visual regression issue that we should discuss privately.

[LuLaValva]

As discussed offline, I have added the standalone-link class which is stylistically identical to nav-link. Examples did not seem necessary, but please let me know if you would like for me to add some to storybook and the skin site.