[fractal] roomlist.rs: replace "favourites" with "favorites"

[Daniel Garcia Moreno <danigm src gnome org>]

commit 50317842379f75d2e398ec744408d107436c5f16
Author: Elizaryev Pavel <gonleef tuta io>
Date:   Mon Jan 14 18:23:48 2019 +0000

    roomlist.rs: replace "favourites" with "favorites"

 fractal-gtk/src/widgets/roomlist.rs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/fractal-gtk/src/widgets/roomlist.rs b/fractal-gtk/src/widgets/roomlist.rs
index 10598e61..d5c69141 100644
--- a/fractal-gtk/src/widgets/roomlist.rs
+++ b/fractal-gtk/src/widgets/roomlist.rs
@@ -427,8 +427,8 @@ impl RoomList {
         );
         let fav = RGroup::new(
             &baseu,
-            i18n("Favourites").as_str(),
-            i18n("Drag and drop rooms here to add them to your favourites").as_str(),
+            i18n("Favorites").as_str(),
+            i18n("Drag and drop rooms here to add them to your favorites").as_str(),
         );
         let rooms = RGroup::new(
             &baseu,