Closes #3482: Update link group paragraph type to use linkit widget.

[joeparsons]

Description

Updates form display settings for experimental link group paragraph type to use linkit widget for link field instead of default core link widget.

Related issues

Closes #3482

How to test

Types of changes

Arizona Quickstart (install profile, custom modules, custom theme)

• Patch release changes
  • [x] Bug fix
  • [ ] Accessibility, performance, or security improvement
  • [ ] Critical institutional link or brand change
  • [ ] Adding experimental module
  • [x] Update experimental module
• Minor release changes
  • [x] New feature
  • [ ] Breaking or visual change to existing behavior
  • [ ] Upgrade experimental module to stable
  • [ ] Enable existing module by default or database update
  • [ ] Non-critical brand change
  • [ ] New internal API or API improvement with backwards compatibility
  • [ ] Risky or disruptive cleanup to comply with coding standards
  • [ ] High-risk or disruptive change (requires upgrade path, risks regression, etc.)
• Other or unknown
  • [ ] Other or unknown

Drupal core

• Patch release changes
  • [ ] Security update
  • [ ] Patch level release (non-security bug-fix release)
  • [ ] Patch removal that's no longer necessary
• Minor release changes
  • [ ] Major or minor level update
• Other or unknown
  • [ ] Other or unknown

Drupal contrib projects

• Patch release changes
  • [ ] Security update
  • [ ] Patch or minor level update
  • [ ] Add new module
  • [ ] Patch removal that's no longer necessary
• Minor release changes
  • [ ] Major level update
• Other or unknown
  • [ ] Other or unknown

Checklist

• [x] My code follows the code style of this project.
• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.
• [x] I have read the CONTRIBUTING document.
• [ ] I have added tests to cover my changes.
• [ ] All new and existing tests passed.

[natebyerley]

Looks to be working well:

https://dev-kitten.pantheonsite.io/test-linkit-nb