[gthumb] Add a missing tag to the AppData file

[Richard Hughes <rhughes src gnome org>]

commit d0b1fa549279548aa8f515478ca5aad48f76ec3c
Author: Richard Hughes <richard hughsie com>
Date:   Mon Jan 25 13:22:03 2016 +0000

    Add a missing tag to the AppData file

 data/appdata/gthumb.appdata.xml.in |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/data/appdata/gthumb.appdata.xml.in b/data/appdata/gthumb.appdata.xml.in
index faf34a6..8f99fd6 100644
--- a/data/appdata/gthumb.appdata.xml.in
+++ b/data/appdata/gthumb.appdata.xml.in
@@ -47,4 +47,5 @@
     <kudo>ModernToolkit</kudo>
     <kudo>UserDocs</kudo>
   </kudos>
+  <project_group>GNOME</project_group>
 </application>