[gnome-builder/wip/gtk4-port] flatpak: Pin appstream dependency

[Christian Hergert <chergert src gnome org>]

commit 8953ad160f617e1bdafdba77d36b68d6875f5737
Author: Günther Wagner <info gunibert de>
Date:   Mon Apr 11 21:30:23 2022 +0200

    flatpak: Pin appstream dependency
    
    their meson requirements are higher then what we have available in
    org.gnome.Platform right now (>= 0.62)

 build-aux/flatpak/org.gnome.Builder.json | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/build-aux/flatpak/org.gnome.Builder.json b/build-aux/flatpak/org.gnome.Builder.json
index 1606744cd..434a6da2c 100644
--- a/build-aux/flatpak/org.gnome.Builder.json
+++ b/build-aux/flatpak/org.gnome.Builder.json
@@ -502,7 +502,7 @@
                 {
                     "type" : "git",
                     "url" : "https://github.com/ximion/appstream.git";,
-                    "branch" : "master"
+                    "commit" : "565ff2f3bcf4497c7ffbd298c95c24ad0b7c3d1e"
                 }
             ]
         },