Fix changelog

Author: Dongwei Wang

src/Synapse/Synapse/ChangeLog.md

@@ -18,7 +18,6 @@
         - 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