Update release notes for v2.1.6-preview (#32)

releasenotes.md

@@ -1,6 +1,8 @@
-# Release 2.1.4-preview
+# Release 2.1.6-preview
 
-- Consume `IOrchestrationService` via dependency injection.
-  - `WithOrchestrationService` now adds to `IServiceCollection` as singleton.
-  - `AddClient` now first looks for `IOrchestrationServiceClient`, then falls back to casting `IOrchestrationService`.
-  - `ITaskHubWorkerBuilder.OrchestrationService` marked as obsolete.
+- Fix `ObjectDisposedException` race condition during orchestration middleware
+  - The fix was to remove the attempt to re-use `IServiceProvider` during sessions of the same orchestration.
+  - The above would only impact if the DTFx orchestration/activity was registered with "Scoped" lifetime.
+  - Doing the above is **strongly not recommended**. It would lead to undeterministic statefulness of your orchestration or activity.
+- Fixed generic type parsing to properly handle nested generics when there are multiple generic arguments.
+- Fix `WrapperOrchestrationContext.IsReplaying` not properly updating.