[gnome-photos] flatpak: Use stable-0.2.x branch of libgfbgraph

[Leesoo Ahn <yisooan src gnome org>]

commit 63aa92ec8eacce712800afa963ee59677cd0e3ad
Author: Leesoo Ahn <yisooan fedoraproject org>
Date:   Sat May 9 18:51:40 2020 +0900

    flatpak: Use stable-0.2.x branch of libgfbgraph
    
    The library has changed the API version to 0.3.x for experiments.
    A lot of changes which may break the API/ABI would come.
    So, still highly recommend to use the 0.2 API version branch.

 flatpak/org.gnome.Photos.json | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/flatpak/org.gnome.Photos.json b/flatpak/org.gnome.Photos.json
index 12a6c69f..9146c954 100644
--- a/flatpak/org.gnome.Photos.json
+++ b/flatpak/org.gnome.Photos.json
@@ -103,6 +103,7 @@
             "sources": [
                 {
                     "type": "git",
+                    "branch": "stable-0.2.x",
                     "url": "https://gitlab.gnome.org/GNOME/libgfbgraph.git";
                 }
             ]