refactor(icons): enabled Firefox lower version 128 support again (#4094)

* refactor(icons): enabled firefox lower version 128 support again

* Update _icon-helpers.scss

Author: mfranzke

packages/foundations/scss/icons/_icon-helpers.scss

@@ -45,7 +45,10 @@ $default-icon-font-size: var(--db-icon-font-size, #{$default-icon-size-rem});
 @mixin icon-content($icon) {
 	content: $icon;
 	// Hiding icon from screenreaders, https://www.w3.org/TR/css-content-3/#alt
-	content: $icon / "";
+	// TODO: remove the @support wrapper as soon as we drop our partly-support for Firefox < version 128 (Enterprise ESR / Extended Support Release; expected to end in 2025, September / https://whattrainisitnow.com/calendar/)
+	@supports (content: ""/"") {
+		content: $icon / "";
+	}
 }
 
 @mixin to-filled-icon() {