UHF-10249: Removed shadow and changed icon size on announcement

[annadruid]

UHF-10249

What was done

• Removed shadow and changed icon size on announcement

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-10249
• Run make drush-cr

How to test

• Create an announcement
• Make sure there isn't a shadow visible anymore
• Make sure the icon is 24x24px
• Check that code follows our standards

Continuous documentation

• This feature has been documented/the documentation has been updated
• This change doesn't require updates to the documentation

Translations

• Translations have been added to .po -files and included in this PR

[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-visual-regression/pull/1224/html_report/

[teroelonen]

This looks good 🦖