Clarify parking ticket presale information

This change was suggested by someone on matrix and sounds reasonable to me, because it increases consistency of the page which says in the faq "parking tickets will be available on-site".

I am not responsible for parking tickets at all, so this change might be factually wrong.

docs/travel.md

@@ -73,7 +73,9 @@ Details are still being worked out.
 Please do not travel via car if you have other options available to you.
 Not just because of your carbon footprint but because handling 2000+ cars and the space they consume is no small task.
 We'd prefere to use the space for villages and cool blinking stuff instead of parking space.
-You will need a [parking ticket](tickets.md) to park your car. Those are sold during the presale and on site for cash.
+You will need a [parking ticket](tickets.md) to park your car.
+Those will be sold on site for cash.
+A presale may happen, but did not until now.
 
 But for some, travel by car is the only viable option, in that case: