[gnome-photos] Update to latest libgd

[Debarshi Ray <debarshir src gnome org>]

commit 1a0a0cfc493347cf66f984e6959ba7c61f4a7e14
Author: Debarshi Ray <debarshir gnome org>
Date:   Thu Jan 26 18:37:28 2017 +0100

    Update to latest libgd
    
    Ensure that GdMainIconBoxChild uses the content-tile style class for
    theming.

 libgd |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/libgd b/libgd
index 58849a8..f7424f6 160000
--- a/libgd
+++ b/libgd
@@ -1 +1 @@
-Subproject commit 58849a8f31a2f99f514a5a5d365f0e9e326a0b18
+Subproject commit f7424f67689d47c332137b9305ff850be2340dbb