Remove unused global variable

src/Form/HmOverviewTerms.php

@@ -29,8 +29,6 @@ class HmOverviewTerms extends OverviewTerms {
    *   The form structure.
    */
   public function buildForm(array $form, FormStateInterface $form_state, VocabularyInterface $taxonomy_vocabulary = NULL) {
-    global $base_path;
-
     // Override the form if the taxonomy hierarchy manager has been set up.
     if (!empty($taxonomy_vocabulary) && $config = \Drupal::config('hierarchy_manager.hmconfig')) {
       if ($allowed_setup_plugins = $config->get('allowed_setup_plugins')) {