LibWeb: Unify check_validity for form associated elements

Author: https://github.com/tete17
Commit: af88a43e9a
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/6024
Reviewed-by: https://github.com/tcl3 ✅

Libraries/LibWeb/HTML/HTMLSelectElement.h

@@ -63,7 +63,6 @@ public:
     Vector<GC::Root<HTMLOptionElement>> list_of_options() const;
 
     bool will_validate();
-    bool check_validity();
 
     // ^EventTarget
     // https://html.spec.whatwg.org/multipage/interaction.html#the-tabindex-attribute:the-select-element