Resolve #3423037 "File without extension"

Closes #3423037

src/Form/SettingsForm.php

@@ -34,7 +34,7 @@ class SettingsForm extends ConfigFormBase {
       '#title' => $this->t('Verification File'),
       '#upload_location' => 'private://applepay',
       '#upload_validators' => [
-        'file_validate_extensions' => [],
+        'FileExtension' => [],
       ],
       '#default_value' => $this->config('apple_pay_verification.settings')->get('verification_file'),
     ];