[Event Hubs] Release Prep (#27993)

The focus of these changes is to prepare the Event Hubs core library for
its April release.

Author: jsquire

sdk/eventhub/Azure.Messaging.EventHubs/CHANGELOG.md

@@ -1,6 +1,6 @@
 # Release History
 
-## 5.7.0-beta.5 (Unreleased)
+## 5.7.0-beta.5 (2022-04-05)
 
 Thank you to our developer community members who helped to make the Event Hubs client libraries better with their contributions to this release:
 
@@ -12,10 +12,6 @@ Thank you to our developer community members who helped to make the Event Hubs c
 
 - An abstract `CheckpointStore` is now available for use with the `PluggableCheckpointStoreEventProcessor<T>` to simplify creating customized event processors and allow reusing existing checkpoint store implementations. 
 
-### Breaking Changes
-
-### Bugs Fixed
-
 ### Other Changes
 
 - Partition key hashing performed by the `EventHubBufferedProducerClient` has been improved for better performance and efficiency.  _(A community contribution, courtesy of [danielmarbach](https://github.com/danielmarbach))_