Update RELEASE_NOTES.md for 1.4.40-RC1 (#268)
Update RELEASE_NOTES.md for 1.4.40-RC1 (#268)

Co-authored-by: Aaron Stannard <5a7a6a189b47cd31d24667a751e4003cd04eced5@petabridge.com>
akkadotnet/Akka.Persistence.MongoDB,Aaronontheweb/Akka.Persistence.MongoDB,akkadotnet/Akka.Persistence.MongoDB,Aaronontheweb/Akka.Persistence.MongoDB