update changelog

Author: awaelchli

CHANGELOG.md

@@ -366,6 +366,9 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 - Fixed gradient accumulation for `DDPShardedPlugin` ([#9122](https://github.com/PyTorchLightning/pytorch-lightning/pull/9122))
 
 
+- Fixed back-compatibility for saving hyperparameters from a single container and inferring its argument name by reverting [#9125](https://github.com/PyTorchLightning/pytorch-lightning/pull/9125) ([#9642](https://github.com/PyTorchLightning/pytorch-lightning/pull/9642))
+
+
 ## [1.4.7] - 2021-09-14
 
 - Fixed logging of nan parameters ([#9364](https://github.com/PyTorchLightning/pytorch-lightning/pull/9364))