Added 1.5.0.1 release notes (#219)

Author: Aaronontheweb

RELEASE_NOTES.md

@@ -1,5 +1,3 @@
-#### 1.5.0 March 2 2023 ####
+#### 1.5.0.1 March 15 2023 ####
 
-Version 1.5.0 is the RTM release of Akka.Logger.Serilog and Akka.NET v1.5.0 RTM integration.
-
-* Updated to [Akka.NET v1.5.0](https://github.com/akkadotnet/akka.net/releases/tag/1.5.0)
+* [Fixed: `SerilogMessageFormatter` CTOR is `private`, can't be instantiated as the default `LogMessageFormatter`](https://github.com/akkadotnet/Akka.Logger.Serilog/issues/217)