Update Users::UpdateService to check for :update_organization_user permission

Summary

The Users::UpdateService currently checks for the wrong permission when validating organization user updates.

Problem

In app/services/users/update_service.rb#L118, the can_update_organization_users? method checks for :update_organization permission:

current_user.can?(:update_organization, organization)

This should instead check for :update_organization_user to properly validate the user's ability to update organization users.

Proposed Solution

Update line 118 to use the correct permission:

current_user.can?(:update_organization_user, organization)