Add '@addtogroup hooks' annotation for hooks in link_attributes.api.php

Problem/Motivation

The hook described in link_attributes.api.php currently violates the Drupal coding standards, because it duplicates the @param in its docblock.

Proposed resolution

Implement a @addtogroup hooks annotation in link_attributes.api.php and fix the Drupal coding standards violations.

Remaining tasks

1. Write a patch
2. Review
3. Commit

User interface changes

None.

API changes

None.

Data model changes

None.