website/docs: add missing breaking change in prompt stages

Signed-off-by: Jens Langhammer <jens.langhammer@beryju.org>

website/docs/releases/v2022.4.md

@@ -9,6 +9,10 @@ slug: "2022.4"
 
   For legacy reasons, authentik used to support HTTP-Basic authenticated requests, using the token as a password. This has been removed.
 
+- Removal of deprecated context in Expression policies used in prompt stages
+
+  Before this version, you could use both `context['*field_name*']` and `context['prompt_data']['*field_name*']`. The former one has been removed as it could overwrite other data in the context if the field name is the same as another context value.
+
 ## New features
 
 - Application Grouping