Update changelog

Author: Dongwei Wang

src/Synapse/Synapse/ChangeLog.md

@@ -18,6 +18,11 @@
         - Additional information about change #1
 -->
 ## Upcoming Release
+* Upgraded Azure.Analytics.Synapse.Artifacts to 1.0.0-preview.9
+* Add support for Synapse Spark job definition
+	- Add `New-AzSynapseSparkJobDefinition` cmdlet
+    - Add `Get-AzSynapseSparkJobDefinition` cmdlet
+    - Add `Remove-AzSynapseSparkJobDefinition` cmdlet
 
 ## Version 0.12.0
 * Upgraded Azure.Analytics.Synapse.Artifacts to 1.0.0-preview.9