Remove deprecated formType from Forms API test

[TomasVotruba]

Description

Companion to mautic/mautic#17082, which removes the long-deprecated form type from Mautic\FormBundle\Entity\Form (deprecated since 7.1, removed in 8.0).

Once core drops the field, form:read responses no longer include formType. FormsTest still sent it in the payload and asserted it back, so it fails against 8.0:

Undefined array key "formType"
tests/Api/FormsTest.php:67

This drops formType from both test payloads.

Compatibility

Safe against older Mautic too:

• Sending formType was already ignored on write (allow_extra_fields => true).
• The field was optional, so omitting it changes nothing on pre-8.0 cores.

             'name'        => 'test',
-            'formType'    => 'standalone',
             'description' => 'API test',

[patrykgruszka]

The change is correct 👍

I think we'll need to figure use the branching model and supported Mautic versions in this repo.

[escopecz]

This is updating just the test which will fail on Mautic 8+. No production change was made. The code will still work for all Mautic versions. The new ones will just reject the outdated payloads. So I see no problem in merging this right away. Some version strategy would be good to have though.