UHF-X: Fix webmanifest favicon url

[Arkkimaagi]

UHF-X

We get favicon errors on main site due to urls being wrong

What was done

• Relative webmanifest file was fixed to be static

How to install

• Make sure your instance is up and running on latest dev branch.
  • git pull origin dev
  • make fresh
• Update the HDBT theme
  • composer require drupal/hdbt:dev-UHF-X_webmanifest_fix
• Run make drush-cr

How to test

• Check that favicons from webmanifest are no longer 404
• Check that code follows our standards

[github-actions]

⚠️ Visual regression found! Please check if this change is wanted or accidental. You can check the output here: https://city-of-helsinki.github.io/drupal-hdbt/pull/1128/html_report/