Remove prefixed abbreviations from top-level menu items

We will remove when we will have clean icon management https://www.drupal.org/project/drupal/issues/3432173 📌 Decide strategy to customize or provide 1st level menu items' icons Active until this it looks impossible.

We need to apply this here for items which does not have icons.
Should be enough imo.

https://dev.to/whitep4nth3r/hide-text-in-css-pseudo-elements-from-screen...

This was a tiny bit tricky b/c we need PostCSS to not mess up the form that is required to provide the empty alt text. Should be OK now. Needs browser testing, but Can I Use shows 91%: https://caniuse.com/?search=content%20alt%20text