[synapse] Add changelog for release (Azure#20867)

* [synapse] Add changelog for release

* Add line ref for Azure#20051

Author: chamons

sdk/synapse/Azure.Analytics.Synapse.AccessControl/CHANGELOG.md

@@ -1,7 +1,8 @@
 # Release History
 
-## 1.0.0-preview.4 (Unreleased)
-
+## 1.0.0-preview.4 (2021-05-11)
+### Key Bug Fixes
+- Updated dependency versions.
 
 ## 1.0.0-preview.3 (2021-02-10)
 

sdk/synapse/Azure.Analytics.Synapse.Artifacts/CHANGELOG.md

@@ -1,7 +1,9 @@
 # Release History
 
-## 1.0.0-preview.9 (Unreleased)
-
+## 1.0.0-preview.9 (2021-05-11)
+### Key Bug Fixes
+- Updated dependency versions.
+- Improved deserialization of optional parameters (https://github.com/Azure/azure-sdk-for-net/issues/20051) 
 
 ## 1.0.0-preview.8 (2021-04-06)
 

sdk/synapse/Azure.Analytics.Synapse.ManagedPrivateEndpoints/CHANGELOG.md

@@ -1,7 +1,8 @@
 # Release History
 
-## 1.0.0-beta.3 (Unreleased)
-
+## 1.0.0-beta.3 (2021-05-11)
+### Key Bug Fixes
+- Updated dependency versions.
 
 ## 1.0.0-beta.2 (2021-02-10)
 

sdk/synapse/Azure.Analytics.Synapse.Monitoring/CHANGELOG.md

@@ -1,7 +1,8 @@
 # Release History
 
-## 1.0.0-beta.3 (Unreleased)
-
+## 1.0.0-beta.3 (2021-05-11)
+### Key Bug Fixes
+- Updated dependency versions.
 
 ## 1.0.0-beta.2 (2021-02-10)
 

sdk/synapse/Azure.Analytics.Synapse.Spark/CHANGELOG.md

@@ -1,7 +1,8 @@
 # Release History
 
-## 1.0.0-preview.6 (Unreleased)
-
+## 1.0.0-preview.6 (2021-05-11)
+### Key Bug Fixes
+- Updated dependency versions.
 
 ## 1.0.0-preview.5 (2021-02-11)
 ### Changed