Update akka-actor, akka-stream to 2.6.15 (#2450)
Update akka-actor, akka-stream to 2.6.15 (#2450)

* Update akka-actor, akka-stream to 2.6.15

* Update akka-actor, akka-stream to 2.6.15
sksamuel/elastic4s,sksamuel/elastic4s