Add upgrade notes

docs/upgrade-notes.asciidoc

@@ -164,5 +164,19 @@ resolving issues if any deprecated features are enabled.
 To access the assistant, go to **Stack Management** > **Upgrade Assistant**.
 
 
+[discrete]
+[[deprecation-202250]]
+.Scripted field creation has been disabled in the Data Views management page (9.0.0)
+[%collapsible]
+====
+*Details* +
+The ability to create new scripted fields has been removed from the *Data Views* management page in 9.0. Existing scripted fields can still be edited or deleted, and the creation UI can be accessed by navigating directly to `/app/management/kibana/dataViews/dataView/{dataViewId}/create-field`, but it is recommended to migrate to runtime fields or ES|QL instead to prepare for removal.
 
+For more information, refer to {kibana-pull}202250[#202250].
 
+*Impact* +
+It will no longer be possible to create new scripted fields directly from the *Data Views* management page.
+
+*Action* +
+Migrate to runtime fields or ES|QL instead of creating new scripted fields. Existing scripted fields can still be edited or deleted.
+====