docs: add changelog entry for pop_views_until

Add new feature record to CHANGELOG.md for v0.85.0 as required
by the release branch CI check.

Author: brunobrown

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ### New features
 
+* Add `Page.pop_views_until()` to pop multiple views and return a result to the destination view ([#6326](https://github.com/flet-dev/flet/issues/6326), [#6347](https://github.com/flet-dev/flet/pull/6347)) by [@brunobrown](https://github.com/brunobrown).
+
 ### Improvements
 
 ### Bug fixes