[gnome-builder] manifest: Switch to new main branch for devhelp module

[Christian Hergert <chergert src gnome org>]

commit fd79bde276d15d1d7f2e2823a18ba895dbf375a8
Author: vanadiae <vanadiae35 gmail com>
Date:   Mon Jul 12 23:23:13 2021 +0200

    manifest: Switch to new main branch for devhelp module
    
    As of this mail on gnome-i18n,
    https://mail.gnome.org/archives/gnome-i18n/2021-July/msg00008.html,
    the "master" branch will be deleted, replaced by "main". Since this will
    caught us later this cycle, better just change to the new branch now.

 build-aux/flatpak/org.gnome.Builder.json | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
---
diff --git a/build-aux/flatpak/org.gnome.Builder.json b/build-aux/flatpak/org.gnome.Builder.json
index 453bf329d..3bfe7f099 100644
--- a/build-aux/flatpak/org.gnome.Builder.json
+++ b/build-aux/flatpak/org.gnome.Builder.json
@@ -313,7 +313,8 @@
             "sources" : [
                 {
                     "type" : "git",
-                    "url" : "https://gitlab.gnome.org/GNOME/devhelp.git";
+                    "url" : "https://gitlab.gnome.org/GNOME/devhelp.git";,
+                    "branch" : "main"
                 }
             ]
         },