Allow chocobo stable training to increase chocobo rank

[Mersilina]

as stated above and more specifically, yea we can gain exp by training our birds in the stables but it cant actually go up a rank without being taken out into the field and summoned for one monster kill. I suggest/request this adjustment because like an idiot I forgot you cant actually gain a rank while stabled and fed it a thavnairian onion when exp bar was full thinking it would increase the rank cap >_>

[FoxyAreku]

It sucks, but it's easy to double check, and there's even a message saying that "No EXP will be gained".

[Zidaryn]

I think this is in place to make you remember that chocobo exp was originally gotten from being summoned in the field. Also could be so that chocobos don't become stable kings/queens.