Rename Aku -> Aku (Samurai Jack)

BUR #8144 has been approved by @nonamethanks.

rename aku -> aku_(samurai_jack)

Ambiguous name, as "aku" means "I" in Indonesian language.
The wiki made it clear that this "aku" is for Samurai Jack character, and some other characters from this series have a qualifier.

I don't think random characters' names being real words in non-english languages is a concern for us. Still, approving this because there's other characters called aku_*.

The bulk update request #8144 (forum #201679) has been approved by @nonamethanks.