Update reference/cubrid/functions/cubrid-prepare.xml

Co-authored-by: Kamil Tekiela <tekiela246@gmail.com>

Author: lacatoire

reference/cubrid/functions/cubrid-prepare.xml

@@ -21,7 +21,7 @@
   <simpara>
       Accordingly, you can use this statement to execute it several times repeatedly or to
       process long data. Only a single statement can be used, and a parameter may be marked with
-      a question mark (?) at the appropriate place in the SQL statement. Add a parameter when you
+      a question mark (<literal>?</literal>) at the appropriate place in the SQL statement. Add a parameter when you
       bind a value in the VALUES clause of an INSERT statement or in the WHERE clause. Note that a
       value can be bound to a MARK(?) only by using the <function>cubrid_bind</function> function.
   </simpara>