[gnome-photos] Update to latest libgd

[Debarshi Ray <debarshir src gnome org>]

commit 98b776a208ca55b6eb1fe0c477b80443a29c0f28
Author: Debarshi Ray <debarshir gnome org>
Date:   Sat Oct 6 17:43:17 2018 +0200

    Update to latest libgd
    
    Silence a deprecation warning with GTK+ 3.16 due to
    gtk_style_context_get_border_color.

 subprojects/libgd | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/subprojects/libgd b/subprojects/libgd
index 7ae254bf..039eff81 160000
--- a/subprojects/libgd
+++ b/subprojects/libgd
@@ -1 +1 @@
-Subproject commit 7ae254bfc5f641c60566614e08245176f7bc5aa8
+Subproject commit 039eff81546b1076bcad5eab5ee6bc37e702e0a5