Migrate milestone filter Bootstrap tabs to GlTabs

What does this MR do and why?

Migrate milestone filter Bootstrap tabs to GlTabs #230757 (closed)

This change updates the classes used to render filter tabs for milestones filters.

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Visit any milestone pages such as
   • http://gdk.test:3000/dashboard/milestones
   • http://gdk.test:3000/groups/h5bp/-/milestones
   • http://gdk.test:3000/h5bp/html5-boilerplate/-/milestones
2. Click on filters such as "Open", "Closed", "All".

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 #230757 (closed)