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/Selector.h

@@ -257,7 +257,7 @@ private:
     Array<u32, 8> m_ancestor_hashes;
 };
 
-String serialize_a_group_of_selectors(Vector<NonnullRefPtr<Selector>> const& selectors);
+String serialize_a_group_of_selectors(SelectorList const& selectors);
 
 }