update changelog

CHANGELOG.md

@@ -334,6 +334,8 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 - Updated several places in the loops and trainer to access `training_type_plugin` directly instead of `accelerator` ([#9901](https://github.com/PyTorchLightning/pytorch-lightning/pull/9901))
 
 
+- Changed default value of the `max_steps` Trainer argument from `None` to -1 ([#9460](https://github.com/PyTorchLightning/pytorch-lightning/pull/9460))
+
 
 ### Deprecated
 
@@ -408,6 +410,10 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 
 - Deprecated `GPUStatsMonitor` and `XLAStatsMonitor` in favor of `DeviceStatsMonitor` callback ([#9924](https://github.com/PyTorchLightning/pytorch-lightning/pull/9924))
 
+
+- Deprecated setting `Trainer(max_steps=None)`. To turn off the limit, set `Trainer(max_steps=-1)` (default) ([#9460](https://github.com/PyTorchLightning/pytorch-lightning/pull/9460))
+
+
 ### Removed
 
 - Removed deprecated `metrics` ([#8586](https://github.com/PyTorchLightning/pytorch-lightning/pull/8586/))