Labels as a facet: Client side for issues - visual bug

What does this MR do and why?

With long multiline label names, there is a visual issue where the label names cover over each other.

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. This MR requires advanced search to be configured and enabled.
2. enable feature flag

   echo 'Feature.enable(:search_issue_label_aggregation)' | rails c

3. Visit the Advanced search page: http://gdk.test:3000/search?scope=issues&search=%2A
4. Scroll in the label dropdown check long label names

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #369541 (closed)