update changelog

Author: DuYicong515

CHANGELOG.md

@@ -530,6 +530,9 @@ 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.num_gpus` in favor of `Trainer.num_devices` when GPU is used. ([#12384](https://github.com/PyTorchLightning/pytorch-lightning/pull/12384))
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 ### Removed
 
 - Removed deprecated parameter `method` in `pytorch_lightning.utilities.model_helpers.is_overridden` ([#10507](https://github.com/PyTorchLightning/pytorch-lightning/pull/10507))
@@ -720,6 +723,9 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 - Removed `AcceleratorConnector.root_gpu` property ([#12262](https://github.com/PyTorchLightning/pytorch-lightning/pull/12262))
 
 
+- Removed `AcceleratorConnector.num_gpus` property ([#12384](https://github.com/PyTorchLightning/pytorch-lightning/pull/12384))
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 ### Fixed
 
 - Fixed an issue where `ModelCheckpoint` could delete older checkpoints when `dirpath` has changed during resumed training ([#12045](https://github.com/PyTorchLightning/pytorch-lightning/pull/12045))