This patch is a follow-up to D2861/rP23804.
* It gives Mauryas a 30% training time discount on elephants. The number is chosen to get theirs under those of the African civs (0.7 × 1.1 = 0.77 < 0.9).
* It explicitly does not affect heroes.
* Elephant archer training time is increased from 20 to 15, to keep it about the same (0.7 × 20 = 14).
* Worker elephant training time is not increased, because it is considered already too high (see D2852).