How do i change this markup from my.theme file?

Line 119 in coremodulessearchsrcControllerSearchController.php

if (count($results)) {
  $build['search_results_title'] = array(
    '#markup' => '<h2>' . $this->t('Search results') . '</h2>',
  );
}

I want to change the “Search results” from my search page.

Drupal version: 


Source: https://www.drupal.org/taxonomy/term/3/feed