Update CHANGELOG.md

Author: darrensmith223

CHANGELOG.md

@@ -6,7 +6,7 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 - [Compare to latest release][unreleased]
 
 ## [1.3.8] - 2021-04-09
-- [#213](https://github.com/SparkPost/python-sparkpost/pull/213) Support for AMP HTML for transmissions
+- [#214](https://github.com/SparkPost/python-sparkpost/pull/214) Support for AMP HTML for transmissions
 
 ## [1.3.7] - 2021-03-24
 - [#211](https://github.com/SparkPost/python-sparkpost/pull/211) Support for top open pixel for transmissions