[polari] Replace GtkPopover:modal property

[Marge Bot <marge-bot src gnome org>]

commit 49a62d495b577696ed16452d09bb24983e49524b
Author: Florian Müllner <fmuellner gnome org>
Date:   Wed Mar 3 18:55:09 2021 +0100

    Replace GtkPopover:modal property
    
    GTK4 renames it to :autohide.
    
    Part-of: <https://gitlab.gnome.org/GNOME/polari/-/merge_requests/228>

 src/tabCompletion.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/src/tabCompletion.js b/src/tabCompletion.js
index 6ee6e1a0..b56a7b5c 100644
--- a/src/tabCompletion.js
+++ b/src/tabCompletion.js
@@ -20,7 +20,7 @@ export default class TabCompletion {
 
         this._popup = new Gtk.Popover({
             position: Gtk.PositionType.TOP,
-            modal: false,
+            autohide: false,
         });
         this._popup.set_parent(this._entry);