fix some typos in Persistence docs
fix some typos in Persistence docs

Silv3rcircl3/akka.net,amichel/akka.net,simonlaroche/akka.net,ali-ince/akka.net,ali-ince/akka.net,simonlaroche/akka.net,Silv3rcircl3/akka.net,heynickc/akka.net,heynickc/akka.net,amichel/akka.net