[libadwaita] doc: Make API changes brought by AdwViewStack more explicit

[Alexander Mikhaylenko <alexm src gnome org>]

commit 27e82dd00c189fd8b9c905d919fa37633144d79b
Author: Adrien Plazas <kekun plazas laposte net>
Date:   Thu Jul 8 16:16:06 2021 +0200

    doc: Make API changes brought by AdwViewStack more explicit

 doc/migrating-libhandy-1-4-to-libadwaita.md | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)
---
diff --git a/doc/migrating-libhandy-1-4-to-libadwaita.md b/doc/migrating-libhandy-1-4-to-libadwaita.md
index 999ae0ba..e0cfab44 100644
--- a/doc/migrating-libhandy-1-4-to-libadwaita.md
+++ b/doc/migrating-libhandy-1-4-to-libadwaita.md
@@ -231,8 +231,11 @@ page objects, similarly to [class@Gtk.Stack]. For example,
 
 [class@Adw.ViewSwitcher], [class@Adw.ViewSwitcherBar] and
 [class@Adw.ViewSwitcherTitle] now use [class@Adw.ViewStack] instead of
-[class@Gtk.Stack]. For the most part, the new widget should be a drop-in
-replacement.
+[class@Gtk.Stack].
+
+You should stop using [property@Gtk.Stack:transition-type] and
+[property@Gtk.Stack:transition-duration] properties before switching to
+[class@Adw.ViewStack].
 
 ### Adapt to [class@Adw.Avatar] API Changes