Turn @staticInterop tear-off into closure

@staticInterop members will start disallowing tear-offs, so this
member should turn into a closure.

Author: srujzs

lib/web_ui/lib/src/engine/text/font_collection.dart

@@ -194,7 +194,9 @@ class FontManager {
     if (_downloadedFonts.isEmpty) {
       return;
     }
-    _downloadedFonts.forEach(domDocument.fonts!.add);
+    for (DomFontFace font in _downloadedFonts) {
+      domDocument.fonts!.add(font);
+    }
   }