Tabs: remove deprecated `routerLink` input

[jakobe]

Which issue does this PR close?

This PR closes #3398

What is the new behavior?

Removes deprecated routerLink property from Tabs.

Does this PR introduce a breaking change?

• [x] Yes
• [ ] No

Are there any additional context?

Checklist:

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Reminders

• [x] Make sure you have implemented tests following the guidelines in: "The good: Test".
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Review

• [x] Determine if your changes are a fix, feature or breaking-change, and add the matching label to your PR. If it is tooling, dependency updates or similar, add ignore-for-release.
• [x] Do a self-review.
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• [ ] Request that the changes are UX reviewed (only necessary if your PR introduces visual changes)

When the pull request has been approved it will be merged to develop by Team Kirby.