Fix changelog date

com.unity.ml-agents/CHANGELOG.md

 and this project adheres to
 [Semantic Versioning](http://semver.org/spec/v2.0.0.html).
 
-## [1.0.5] - 2020-09-2
+## [1.0.5] - 2020-09-23
 ### Minor Changes
 #### com.unity.ml-agents (C#)
 - Update Barracuda to 1.0.3. (#4506)