Issue #3440115 by mondrake: Change remaining File module test dataproviders to static

(cherry picked from commit 11fb273f93cb61e874ce0aa49949def90d9984da)

core/modules/file/tests/src/Functional/Formatter/FileMediaFormatterTestBase.php

@@ -86,7 +86,7 @@ abstract class FileMediaFormatterTestBase extends BrowserTestBase {
    *     - The number of expected HTML tags.
    *     - An array of settings for the field formatter.
    */
-  public function dataProvider() {
+  public static function dataProvider(): array {
     return [
       [2, []],
       [1, ['multiple_file_display_type' => 'sources']],