LibWeb: Remove broken CSS:Parser::is_combinator()

A single DELIM token is only one character long, so the check for
a "||" DELIM didn't work. We now just do the check inline.

Userland/Libraries/LibWeb/CSS/Parser/Parser.h

@@ -69,7 +69,6 @@ private:
     Token peek_token();
     Token current_token();
     void reconsume_current_input_token();
-    bool is_combinator(String);
 
     NonnullRefPtrVector<QualifiedStyleRule> consume_a_list_of_rules(bool top_level);
     NonnullRefPtr<AtStyleRule> consume_an_at_rule();