Update CHANGELOG.md

Co-authored-by: Carlos Mocholí <[email protected]>

Author: tchaton

CHANGELOG.md

@@ -109,8 +109,6 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 - Fixed error thrown when using valid distributed mode in multi node ([#6297](https://github.com/PyTorchLightning/pytorch-lightning/pull/6297)
 
 
-- Added `checkpoint` parameter to callback's `on_save_checkpoint` hook ([#6072](https://github.com/PyTorchLightning/pytorch-lightning/pull/6072))
-
 ## [1.2.1] - 2021-02-23
 
 ### Fixed