clear release notes post 2.8.0 release (#2268)

Author: davidmrdavid

release_notes.md

@@ -1,12 +0,0 @@
-## Bug Fixes
-- Correctly Serialize HostStoppingEvent in ActivityShim (https://github.com/Azure/azure-functions-durable-extension/pull/2178)
-- Fix NotImplementedException for management API calls from Java client (https://github.com/Azure/azure-functions-durable-extension/pull/2193)
-- Handle OOM and other exceptions in entity shim by aborting the session (https://github.com/Azure/azure-functions-durable-extension/pull/2234)
-
-## Enhancements
-- add optional 'instanceIdPrefix' query parameter to the HTTP API for instance queries
-
-## Dependencies
-- DurableTask.Core --> v2.10.*
-- DurableTask.AzureStorage --> v1.12.*
-- DurableTask.Analyzers --> 0.5.0