Issue #2854586 by NonProfit: Stark's helptext link redirects to D7 theme guide

core/themes/stark/stark.info.yml

 name: Stark
 type: theme
-description: 'An intentionally plain theme with no styling to demonstrate default Drupal’s HTML and CSS. Learn how to build a custom theme from Stark in the <a href="https://www.drupal.org/theme-guide">Theming Guide</a>.'
+description: 'An intentionally plain theme with no styling to demonstrate default Drupal’s HTML and CSS. Learn how to build a custom theme from Stark in the <a href="https://www.drupal.org/docs/8/theming">Theming Guide</a>.'
 package: Core
 version: VERSION
 core: 8.x