Remove unused underline prop from LinkButtonProps

[liuliu-dev]

Closes #7173

Changelog

Removes the unused underline prop from LinkButtonProps in the LinkButton component.

Rollout strategy

• Patch release

Testing & Reviewing

Merge checklist

• Added/updated tests
• Added/updated documentation
• Added/updated previews (Storybook)
• Changes are SSR compatible
• Tested in Chrome
• Tested in Firefox
• Tested in Safari
• Tested in Edge
• (GitHub staff only) Integration tests pass at github/github (Learn more about how to run integration tests)

[changeset-bot]

🦋 Changeset detected

Latest commit: d735b21

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@primer/react	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[github-actions]

👋 Hi, this pull request contains changes to the source code that github/github-ui depends on. If you are GitHub staff, test these changes with github/github-ui using the integration workflow. Or, apply the integration-tests: skipped manually label to skip these checks.

[primer-integration]

👋 Hi from github/github-ui! Your integration PR is ready: https://github.com/github/github-ui/pull/6728

[Copilot]

Pull Request Overview

This PR removes the unused underline prop from the LinkButtonProps type definition, cleaning up the API surface by removing a property that was never implemented or used in the LinkButton component.

Key Changes

• Removed the unused underline?: boolean property from LinkButtonProps type definition
• Added a changeset documenting this as a patch release

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
packages/react/src/Button/types.ts	Removes the unused underline property from LinkButtonProps type definition
.changeset/short-lands-create.md	Adds changeset entry documenting the removal as a patch release

[Copilot]

This change removes a prop from a public TypeScript interface, which is technically a breaking change for TypeScript consumers who may have been passing this prop (even though it had no runtime effect). This should be released as a 'minor' version instead of a 'patch' to follow semantic versioning conventions for breaking changes in TypeScript APIs.

Suggested change

	'@primer/react': patch
	'@primer/react': minor

[primer-integration]

🟢 ci completed with status success.

[francinelucca]