Update to use family-linked webfonts and stop using mixins

[Scotchester]

Switches from using our old u-webfont- mixins to simple CSS styling, in accordance with the current version of Capital Framework which defaults to family-linked webfonts.

Changes

• All u-webfont- mixins converted to simple CSS styling

Removals

• @webfont- variables that duplicated the ones now in CF.

Testing

1. Pull branch
2. grunt
3. bundle exec jekyll serve watch
4. Visit http://localhost:4000/ and browse around; see fonts looking as they should

Preview this PR without the whitespace changes

Checklist

• [ ] Changes are limited to a single goal (no scope creep)
• [ ] Code can be automatically merged (no conflicts)
• [ ] Code follows the standards laid out in the front end playbook
• [ ] Passes all existing automated tests
• [ ] New functions include new tests
• [ ] New functions are documented (with a description, list of inputs, and expected output)
• [ ] Placeholder code is flagged
• [ ] Visually tested in supported browsers and devices
• [ ] Project documentation has been updated (including the "Unreleased" section of the CHANGELOG)

[jimmynotjim]

Searched the repo and it looks like you found them all. At this point can we remove all references to the mixins from cf-core?

[Scotchester]

Searched the repo and it looks like you found them all. At this point can we remove all references to the mixins from cf-core?

Probably? I'm sure there are projects still using them, but as long as we do a major version update, that shouldn't be a big deal.

[jimmynotjim]

I'm sure there are projects still using them, but as long as we do a major version update, that shouldn't be a big deal.

Shoot, we should have included this in the v5 release. We'll have to make sure we don't forget when we remove the icon font in v6.