[Form] Bad setUp prototype in form unit testing

[ruano-a]

In this page https://symfony.com/doc/current/form/unit_testing.html#testings-types-registered-as-services

The function setUp is not defined with a void return type.
This causes an error :

Fatal error: Declaration of App\Tests\Unit\Form\MyTest::setUp() must be compatible with Symfony\Component\Form\Test\TypeTestCase::setUp(): void in MyTest.php