LibWeb/CSS: Use SelectorList type instead of Vector<NNRP<Selector>>

Author: https://github.com/AtkinsSJ
Commit: 74c448d744
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/1842
Reviewed-by: https://github.com/awesomekling

Userland/Libraries/LibWeb/CSS/Parser/SelectorParsing.cpp

@@ -65,7 +65,7 @@ Parser::ParseErrorOr<SelectorList> Parser::parse_a_selector_list(TokenStream<T>&
 {
     auto comma_separated_lists = parse_a_comma_separated_list_of_component_values(tokens);
 
-    Vector<NonnullRefPtr<Selector>> selectors;
+    SelectorList selectors;
     for (auto& selector_parts : comma_separated_lists) {
         auto stream = TokenStream(selector_parts);
         auto selector = parse_complex_selector(stream, mode);