jdk12 and jdk13 java api docs disappeared

[Martin Buchholz]

https://jdk.java.net/13/ points to
https://download.java.net/java/early_access/jdk13/docs/api/
but that's a 404

Similarly for
https://jdk.java.net/12/ =>
https://download.java.net/java/early_access/jdk12/docs/api/