LibWeb: Make StyleSheetList GC-allocated

Author: https://github.com/awesomekling
Commit: 5366924f11
Pull-request: https://github.com/SerenityOS/serenity/pull/14816
Reviewed-by: https://github.com/ADKaster
Reviewed-by: https://github.com/linusg ✅

Userland/Libraries/LibWeb/CSS/StyleComputer.cpp

@@ -140,7 +140,7 @@ void StyleComputer::for_each_stylesheet(CascadeOrigin cascade_origin, Callback c
     }
     if (cascade_origin == CascadeOrigin::Author) {
         for (auto const& sheet : document().style_sheets().sheets()) {
-            callback(*sheet);
+            callback(sheet);
         }
     }
 }