[examiner] Only show active examiner sites

[CamilleBeau]

Brief summary of changes

In this PR, only active examiner sites are shown for an examiner in the examiner module. Previously, the module was showing any site that the examiner had once been an examiner at, whether it was active or not.

• Have you updated related documentation?

Testing instructions (if applicable)

1. Add a user as an examiner setting several examiner sites
2. Remove some sites from the examiner
3. Load the examiner module and search for the user
4. Make sure that only sites that are still active are shown in the examiner module

Link(s) to related issue(s)

• Resolves [User account] Removing sites at which a user is an examiner does not seem to work #5768