It is said that multi-step forms should have form navigation in them. But is it also needed in 2-step forms?
Yes, the number of steps should be clearly indicated.
When a user fills up a form, he or she doesn't know that there are just two forms. Such awareness affects positively on user's decision whether or not to proceed with filling up a form.
If the steps are small and can be combined, perhaps, it can be an even better option. In this case, don't forget to update the title of the button from "Next" to "Finish", that will indicate that the form contains no additional steps.