LibJS: Port remaining bytecode identifiers to UTF-16

Author: https://github.com/trflynn89
Commit: cf61171864
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/5845
Reviewed-by: https://github.com/gmta ✅

Libraries/LibJS/Bytecode/Generator.h

@@ -212,11 +212,6 @@ public:
         return m_regex_table->insert(move(regex));
     }
 
-    IdentifierTableIndex intern_identifier(FlyString const& string)
-    {
-        return intern_identifier(Utf16FlyString::from_utf8(string));
-    }
-
     IdentifierTableIndex intern_identifier(Utf16FlyString string)
     {
         return m_identifier_table->insert(move(string));