Libraries: Use default constructors/destructors in LibWeb

https://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#cother-other-default-operation-rules

"The compiler is more likely to get the default semantics right and
you cannot implement these functions better than the compiler."

Userland/Libraries/LibWeb/HTML/HTMLHtmlElement.cpp

@@ -13,9 +13,7 @@ HTMLHtmlElement::HTMLHtmlElement(DOM::Document& document, DOM::QualifiedName qua
 {
 }
 
-HTMLHtmlElement::~HTMLHtmlElement()
-{
-}
+HTMLHtmlElement::~HTMLHtmlElement() = default;
 
 bool HTMLHtmlElement::should_use_body_background_properties() const
 {