Update qa-selector to testid for admin overview groups users

What does this MR do and why?

Updating qa-selector to testid for the following pages:

• Admin Overview Groups
• Admin Overview Users

This is joint effort based on gitlab-org/quality/quality-engineering/team-tasks#1735 (closed)

Related issue to this specific MR - gitlab-org/quality/quality-engineering/team-tasks#2005 (closed)

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.