Mentions should not highlight the email address on matches

Summary

The mentions feature currently does not take into account email addresses to match against the input from the user.

However, it highlights this in the results leading to confusion for the end user.

1. - Go to a JIRA issue.
2.- Create a user (username=admin, email=admin@example.com)
3.- Start a comment and type " @adm".
4.- Notice that in the results dropdown both the username and email are highlighted even though only usernames are taking into account by the search.

Expected Results

JIRA should not highlight the email address as it's not part of the search criteria.

Actual Results

Both username and email are highlighted by the dropdown.