LibWeb/CSS: Clarify comment about cascading presentational hints

The spec allows us to either treat them as part of the UA origin, or as
its own origin before author styles. This second behaviour turns out to
be what we are currently doing, which is nice!

Funnily enough this was clarified in the spec barely a month after this
original comment was written. :^)

Userland/Libraries/LibWeb/CSS/StyleComputer.cpp

@@ -1551,7 +1551,12 @@ void StyleComputer::compute_cascaded_values(StyleProperties& style, DOM::Element
     previous_layer_style = style.clone();
     cascade_declarations(style, element, pseudo_element, matching_rule_set.user_rules, CascadeOrigin::User, Important::No, previous_origin_style, previous_layer_style);
 
-    // Author presentational hints (NOTE: The spec doesn't say exactly how to prioritize these.)
+    // Author presentational hints
+    // The spec calls this a special "Author presentational hint origin":
+    // "For the purpose of cascading this author presentational hint origin is treated as an independent origin;
+    // however for the purpose of the revert keyword (but not for the revert-layer keyword) it is considered
+    // part of the author origin."
+    // https://drafts.csswg.org/css-cascade-5/#author-presentational-hint-origin
     previous_origin_style = style.clone();
     if (!pseudo_element.has_value()) {
         element.apply_presentational_hints(style);