Proof that Harry Potter and the Cursed Child is Not Canon

[Arnox]

Was rereading Order of the Phoenix and I came across a passage in it. So, as we all know, it is pretty much confirmed that anything Professor Trelawney says will happen actually does happen. And in Chapter 26 of The Order of the Phoenix, Trelawney says the following,

... Professor Trelawney broke into hysterical sobs during Divination and announced to the startled class, and a very disapproving Umbridge, that Harry was not going to suffer an early death after all, but would live to a ripe old age, become Minister of Magic, and have twelve children.

So, despite what Rowling herself may say, by the rules of her own universe, The Cursed Child technically cannot be canon.