Update article pagination to use new theme variables

[jmuzina]

Done

Updates Article Pagination pattern to use new theme variables.

This affects:

• Color of the previous/next button text. It now uses the default text color.
• Color of the previous/next button chevrons. It now uses the default icon color.

Fixes WD-11864

While working on this, I also noticed that the back/next buttons can be updated to use the new chevron left/right code, and made #5125.

QA

• Open demo.
• Verify that the color of all text & chevrons is correct in all themes.

Check if PR is ready for release

If this PR contains Vanilla SCSS code changes, it should contain the following changes to make sure it's ready for the release:

• PR should have one of the following labels to automatically categorise it in release notes:
  • Feature 🎁, Breaking Change 💣, Bug 🐛, Documentation 📝, Maintenance 🔨.
• Vanilla version in package.json should be updated relative to the most recent release, following semver convention:
  • if CSS class names are not changed it can be bugfix relesase (x.x.X)
  • if CSS class names are changed/added/removed it should be minor version (x.X.0)
  • see the wiki for more details
• Any changes to component class names (new patterns, variants, removed or added features) should be listed on the what's new page.

Screenshots

Before:

After:

[webteam-app]

Demo

Jenkins

demos.haus

[jmuzina]

Percy build shows minor difference to the left & right chevrons as expected. It doesn't currently capture light/dark/paper screenshots however.

[jmuzina]

@lyubomir-popov Please verify that the colors in the demo are correct