Update LinkStyles.php
Use the matcher pattern 'classes' key per https://ckeditor.com/docs/ckeditor5/latest/support/error-codes.html#error-matcher-pattern-deprecated-attributes-class-key. Also, provide (possibly) multiple classes as array rather than imploded string per https://ckeditor.com/docs/ckeditor5/latest/api/module_engine_view_matcher-MatcherPattern.html.
Closes #3405556