fix: redirecting to team members when there are not roles left after removing the last one

[jacobo-dominguez-wgu]

Description

Adding validation to redirect to team members table after being on the audit user page and removing the last assigned role to the user.

Scenario: Removing the last role redirects to Team Members
Given I open the audit view for a user with only one role assignment
When I click the trash icon and confirm
Then a success toast appears, I am redirected to the Team Members table, and the user no longer appears there

It closes #147

Demo

Grabacion.de.pantalla.2026-04-27.a.la.s.11.02.53.a.m.mov

How to test it

1. Go to a specific user page with roles assigned http://apps.local.openedx.io:2025/admin-console/authz/user/:userId
2. Remove all the roles assigned.
3. Once the last role is removed, it must redirect to the team members view.

[openedx-webhooks]

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.47%. Comparing base (bceb3c0) to head (509dfff).
⚠️ Report is 3 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #146   +/-   ##
=======================================
  Coverage   97.46%   97.47%           
=======================================
  Files          89       89           
  Lines        2133     2135    +2     
  Branches      461      462    +1     
=======================================
+ Hits         2079     2081    +2     
  Misses         52       52           
  Partials        2        2           

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[rodmgwgu]

Tested and working as expected, thanks for the quick turnaround!