ISTWCMS-4729:additional class to match the expected css

src/Form/UwSearchForm.php

@@ -63,7 +63,7 @@ class UwSearchForm extends FormBase {
       '#type' => 'select',
       '#id' => 'uw-select-site',
       '#attributes' => [
-        'class' => ['uw-select--search'],
+        'class' => ['form-item__select', 'uw-select--search'],
       ],
       '#options' => [
         '' => $this->t('On all sites'),