feat(link): update styling of skip link variant - FE-6719

[DipperTheDan]

Proposed behaviour

Current behaviour

Checklist

• Commits follow our style guide
• Related issues linked in commit messages if required
• Screenshots are included in the PR if useful
• All themes are supported if required
• Unit tests added or updated if required
• Playwright automation tests added or updated if required
• Storybook added or updated if required
• Translations added or updated (including creating or amending translation keys table in storybook) if required
• Typescript d.ts file added or updated if required
• Related docs have been updated if required

QA

• Tested in provided StackBlitz sandbox/Storybook
• Add new Playwright test coverage if required
• Carbon implementation matches Design System/designs
• UI Tests GitHub check reviewed if required

Additional context

I have removed the styling tests in RTL for the skip link variant. The tests used toHaveStyle assertion with token values and we have come to learn these tests don't really work as they always pass. These styles are better tested in Playwright, which we already had.

Testing instructions

• SkipLink should match the designs provided on the ticket.
• There should not be any other styling regressions with Link.

[carbonci]

🎉 This PR is included in version 142.1.0 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot 📦🚀