[synapse] Changelog for Spark StartCreateSparkStatement release patch (Azure#18693)

Author: chamons

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

@@ -1,7 +1,8 @@
 # Release History
 
-## 1.0.0-preview.5 (Unreleased)
-
+## 1.0.0-preview.5 (2021-02-11)
+### Changed
+- Fix StartCreateSparkStatement API visibility
 
 ## 1.0.0-preview.4 (2021-02-10)