feat: show placeholders for individual date parts in date of birth field

src/Form/BookingParticipantType.php

@@ -171,11 +171,6 @@ class BookingParticipantType extends AbstractType
                 'attr' => [
                     'class' => 'flex items-center space-x-2',
                 ],
-                'placeholder' => [
-                    'year' => 'Jahr',
-                    'month' => 'Monat',
-                    'day' => 'Tag',
-                ],
             ], $getFieldState('dateOfBirth')))
             ->add('gender', ChoiceType::class, $this->mergeFieldState([
                 'label' => 'Geschlecht',