LibWeb: Prefix AK::Duration with AK Namespace

Author: https://github.com/ADKaster
Commit: b20a1d0fcd
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/676
Reviewed-by: https://github.com/AtkinsSJ ✅
Reviewed-by: https://github.com/trflynn89 ✅

Userland/Libraries/LibWeb/HTML/HTMLFormElement.cpp

@@ -957,7 +957,7 @@ Vector<FlyString> HTMLFormElement::supported_property_names() const
             Name,
             Past,
         } source;
-        Duration age;
+        AK::Duration age;
     };
     Vector<SourcedName> sourced_names;