LibWeb: Fix a few const-ness issues

Author: https://github.com/mattco98
Commit: c0b2fa74ac
Pull-request: https://github.com/SerenityOS/serenity/pull/17620
Issue: https://github.com/SerenityOS/serenity/issues/16988
Reviewed-by: https://github.com/ADKaster ✅
Reviewed-by: https://github.com/linusg

Userland/Libraries/LibWeb/HTML/Parser/HTMLParser.h

@@ -119,7 +119,7 @@ private:
 
     void generate_implied_end_tags(DeprecatedFlyString const& exception = {});
     void generate_all_implied_end_tags_thoroughly();
-    JS::NonnullGCPtr<DOM::Element> create_element_for(HTMLToken const&, DeprecatedFlyString const& namespace_, DOM::Node const& intended_parent);
+    JS::NonnullGCPtr<DOM::Element> create_element_for(HTMLToken const&, DeprecatedFlyString const& namespace_, DOM::Node& intended_parent);
 
     struct AdjustedInsertionLocation {
         JS::GCPtr<DOM::Node> parent;