Update RELEASE_NOTES.md for 1.5.43 release

[Arkatufus]

1.5.43 June 10th, 2025

Akka.NET v1.5.43 contains several bug fixes and also adds new quality of life features.

• Cluster.Tools: Fix PublishWithAck response message type
• Sharding: Allows sharding delivery consumer to passivate self
• TestKit: Fix CallingThreadDispatcher async context switching
• Persistence.Query: Add non-generic ReadJournalFor API method
• Core: Simplify null checks
• Core: Propagate CoordinatedShutdown reason to application exit code
• Core: Bump AkkaAnalyzerVersion to 0.3.3
• Core: Improve IScheduledTellMsg DeadLetter log message

New Akka.Analyzer Rules

We've added three new Akka.Analyzer rules, AK2003, AK2004, and AK2005. All of them addresses the same Akka anti-pattern where a void async delegate is being passed into the ReceiveActor.Receive<T>() (AK2003), IDslActor.Receive<T>() (AK2004), and ReceivePersistentActor.Command<T>() (AK2005) message handlers.

Here are the documentation for each new rules:

• AK2003 documentation
• AK2004 documentation
• AK2005 documentation

4 contributors since release 1.5.42

COMMITS	LOC+	LOC-	AUTHOR
7	435	19	Gregorius Soedharmo
2	26	23	Mark Dinh
1	49	136	Simon Cropp
1	4	0	Aaron Stannard

To see the full set of changes in Akka.NET v1.5.43, click here.