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/DOM/Comment.cpp

@@ -15,10 +15,6 @@ Comment::Comment(Document& document, const String& data)
 {
 }
 
-Comment::~Comment()
-{
-}
-
 // https://dom.spec.whatwg.org/#dom-comment-comment
 NonnullRefPtr<Comment> Comment::create_with_global_object(Bindings::WindowObject& window, String const& data)
 {