[gtk/ebassi/for-master] docs: Add note for the removal of GtkFileChooserButton

[Emmanuele Bassi <ebassi src gnome org>]

commit 08d52bee14d6c461aefaa8ff8aaef5dbc215e3f1
Author: Emmanuele Bassi <ebassi gnome org>
Date:   Mon Dec 14 16:55:15 2020 +0000

    docs: Add note for the removal of GtkFileChooserButton
    
    Point developers in the direction of GtkButton and GtkFileChooserNative.

 docs/reference/gtk/migrating-3to4.md | 8 ++++++++
 1 file changed, 8 insertions(+)
---
diff --git a/docs/reference/gtk/migrating-3to4.md b/docs/reference/gtk/migrating-3to4.md
index c4024c9c2f..461be38197 100644
--- a/docs/reference/gtk/migrating-3to4.md
+++ b/docs/reference/gtk/migrating-3to4.md
@@ -1149,6 +1149,14 @@ pointer coordinates as inout arguments any more, but as normal in ones.
 
 See: gtk_tree_view_get_tooltip_context(), gtk_icon_view_get_tooltip_context()
 
+### Stop using GtkFileChooserButton
+
+The `GtkFileChooserButton` widget was removed, due to its shortcomings in
+the user interaction. You can replace it with a simple #GtkButton that
+shows a #GtkFileChooserNative dialog when clicked; once the file selection
+has completed, you can update the label of the #GtkButton with the selected
+file.
+
 ## Changes to consider after the switch
 
 GTK 4 has a number of new features that you may want to take