MiqAeTools#form_field_changed spec - reintroduce test for target_class=''
MiqAeTools#form_field_changed spec - reintroduce test for target_class=''

The test was both broken and removed by https://github.com/ManageIQ/manageiq/pull/10060.

Reintroducing.

ManageIQ/manageiq-ui-classic,ManageIQ/manageiq-ui-classic,ManageIQ/manageiq-ui-classic,ManageIQ/manageiq-ui-classic