Use gl_tabs_nav helper for integration overrides

What does this MR do and why?

To support the GlTab migration epic &3983, this MR updates the Integration Overrides tabs to use the new gl_tabs_nav helper introduced in !70919 (merged).

We were already using the gitlab-ui styles, so there should be no visible changes.

Screenshots or screen recordings

Admin-level (first tab)

Before	After

Admin-level (second tab)

Before	After

Group-level

Before	After

Project-level

Before	After

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

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.