updated changelog

changelog.md

@@ -3,9 +3,9 @@ Changelog
 Changes since Flatland 2.1.0
 --------------------------
 
-### Changes in 'scheulde_generators'
+### Changes in 'schedule_generators'
 - Schedule generators now provide the max number of steps allowed per episode
-
+- Pickle files generated with older versions of Flatland need to be regenerated in order to include `_max_episode_steps`
 Changes since Flatland 2.0.0
 --------------------------
 ### Changes in `EnvAgent`