[gnome-photos] Add a missing tag to the AppData file

[Richard Hughes <rhughes src gnome org>]

commit d85048a8342a1f9b189cb799827ffb5b013e5af7
Author: Richard Hughes <richard hughsie com>
Date:   Mon Jan 25 13:05:33 2016 +0000

    Add a missing tag to the AppData file

 data/org.gnome.Photos.appdata.xml.in |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/data/org.gnome.Photos.appdata.xml.in b/data/org.gnome.Photos.appdata.xml.in
index f07a19d..d13aa61 100644
--- a/data/org.gnome.Photos.appdata.xml.in
+++ b/data/org.gnome.Photos.appdata.xml.in
@@ -41,4 +41,5 @@
   </screenshots>
   <url type="homepage">https://wiki.gnome.org/Apps/Photos</url>
   <updatecontact>debarshir_at_gnome.org</updatecontact>
+  <project_group>GNOME</project_group>
 </application>