fix changelog link

Author: DuYicong515

CHANGELOG.md

@@ -527,6 +527,8 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 - Deprecated `Trainer.root_gpu` in favor of `Trainer.strategy.root_device.index` when GPU is used. ([#12262](https://github.com/PyTorchLightning/pytorch-lightning/pull/12262))
 
 
+- Deprecated `Trainer.root_gpu` in favor of `Trainer.strategy.root_device.index` when GPU is used. ([#12262](https://github.com/PyTorchLightning/pytorch-lightning/pull/12262))
+
 
 ### Removed