[geary] flatpak: Fix branch name

[Cédric Bellegarde <cbellegarde src gnome org>]

commit 0d066955b70e5f00f540ec244246130ac6237b43
Author: Cédric Bellegarde <cedric bellegarde adishatz org>
Date:   Wed Aug 3 21:49:52 2022 +0200

    flatpak: Fix branch name

 org.gnome.Geary.json | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/org.gnome.Geary.json b/org.gnome.Geary.json
index 08a714c2e..5fa83d511 100644
--- a/org.gnome.Geary.json
+++ b/org.gnome.Geary.json
@@ -273,7 +273,7 @@
                 {
                     "type": "git",
                     "url": "https://gitlab.gnome.org/GNOME/geary.git";,
-                    "branch": "mainline"
+                    "branch": "main"
                 }
             ]
         }