Berath's Challenge - Kills refresh timer

[Lamppost in Winter]

https://www.nexusmods.com/pillarsofeternity2/mods/364

Made a little tweak to Berath's Challenge. Thought it was a bit harsh on the lower levels when you don't have any way of reviving, and there's almost no way you can finish a combat in 3 rounds. Killing enemies will now refresh the timer before the party member is permanently killed.