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

[Richard Hughes <rhughes src gnome org>]

commit 2b6e834f58eae9dacd375ecc248b17689c0d5249
Author: Richard Hughes <richard hughsie com>
Date:   Mon Jan 25 13:23:32 2016 +0000

    Add a missing tag to the AppData file

 src/org.gnome.Screenshot.appdata.xml.in |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/src/org.gnome.Screenshot.appdata.xml.in b/src/org.gnome.Screenshot.appdata.xml.in
index c6dde8e..4543f99 100644
--- a/src/org.gnome.Screenshot.appdata.xml.in
+++ b/src/org.gnome.Screenshot.appdata.xml.in
@@ -31,4 +31,5 @@
     <kudo>ModernToolkit</kudo>
   </kudos>
   <updatecontact>richard hughsie com</updatecontact>
+  <project_group>GNOME</project_group>
 </application>