Update LUA Riki BackStab ability to use its talent

[darklordabc]

Riki is meant to have a talent that multiples the damage from backstab, but we don't use the original ability, we use a recreated ability which unfortunately does not work with the talent Somebody needs to go into this file https://github.com/darklordabc/Legends-of-Dota-Redux/blob/develop/src/game/scripts/vscripts/abilities/riki_backstab_lod.lua and make the ability check for the talent, after that we can set the LUA backstab as a linked ability talent in npc_abilities_override file

[Wouterz90]

#1570

Haven't tested it