Update changelog

Author: adamreeve

src/lightning/pytorch/CHANGELOG.md

@@ -16,6 +16,8 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 
 - Fix CSVLogger logging hyperparameter at every write which increase latency  ([#20594](https://github.com/Lightning-AI/pytorch-lightning/pull/20594))
 
+- Fix OverflowError when resuming from checkpoint with an iterable dataset ([#20565](https://github.com/Lightning-AI/pytorch-lightning/issues/20565))
+
 
 ## [2.5.0] - 2024-12-19