Update release date (Azure#13939)

Author: joheredi

sdk/core/abort-controller/CHANGELOG.md

@@ -1,8 +1,8 @@
 # Release History
 
-## 1.0.3 (Unreleased)
+## 1.0.3 (2021-02-23)
 
-- Support Typescript version < 3.6 by down-leveling the type definition files. ([PR 12793](https://github.com/Azure/azure-sdk-for-js/pull/12793))
+Support Typescript version < 3.6 by down-leveling the type definition files. ([PR 12793](https://github.com/Azure/azure-sdk-for-js/pull/12793))
 
 ## 1.0.2 (2020-01-07)