Setting provider method to static

Provider method signature is different from the parent - defining the child method as static resolves the issue.

tests/src/Kernel/UpgradePathTest.php

@@ -133,7 +133,7 @@ class UpgradePathTest extends SmartDefaultSettingsTest {
   /**
    * {@inheritdoc}
    */
-  public function provider() {
+  public static function provider() {
     $expected_ckeditor5_toolbar = [
       'items' => [
         'bold',