LibWeb: Replace usages of dynamic_cast with as and as_if

Author: https://github.com/tcl3
Commit: aadd563592
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/5953
Reviewed-by: https://github.com/gmta ✅
Reviewed-by: https://github.com/trflynn89

Libraries/LibWeb/HTML/PopoverInvokerElement.cpp

@@ -95,8 +95,7 @@ GC::Ptr<HTMLElement> PopoverInvokerElement::get_the_popover_target_element(GC::R
         return {};
 
     // 4. Let popoverElement be the result of running node's get the popovertarget-associated element.
-    auto const* popover_invoker_element = dynamic_cast<PopoverInvokerElement const*>(node.ptr());
-    VERIFY(popover_invoker_element);
+    auto const* popover_invoker_element = as_if<PopoverInvokerElement>(*node);
     GC::Ptr<HTMLElement> popover_element = as<HTMLElement>(popover_invoker_element->m_popover_target_element.ptr());
     if (!popover_element) {
         auto target_id = as<HTMLElement>(*node).attribute("popovertarget"_fly_string);