I'm using Drupal 8, this worked for me.

In ***/core/modules/views/views.theme.inc*** file I appended following code to ***template_preprocess_views_view*** method:

   

    $view = $variables['view'];
    $id = $view->storage->id();
    
    ...
    ...
    ...
    
    if( $id == '__VIEW_ID__' && $view->args[0]) {
    
        // Get tid from contextual argument of the view
        $tid = $view->args[0];
    
        // Load the Term Entity
        $term = \Drupal::entityTypeManager()->getStorage('taxonomy_term')->load($tid);
        // $term = Term::load($tid);
    
        // Term Title
        $new_title = $term->getName();
    
        // Set the new Page Title
        $request = \Drupal::request();
        if ($route = $request->attributes->get(\Symfony\Cmf\Component\Routing\RouteObjectInterface::ROUTE_OBJECT)) {
          $route->setDefault('_title', $new_title);
        }
     }