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

[Richard Hughes <rhughes src gnome org>]

commit fafa30c550a6e9d15bf3f84890056ead5eab2de4
Author: Richard Hughes <richard hughsie com>
Date:   Mon Jan 25 13:04:42 2016 +0000

    Add a missing tag to the AppData file

 data/appdata/gnome-power-statistics.appdata.xml.in |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/data/appdata/gnome-power-statistics.appdata.xml.in 
b/data/appdata/gnome-power-statistics.appdata.xml.in
index ca7bb35..5471a01 100644
--- a/data/appdata/gnome-power-statistics.appdata.xml.in
+++ b/data/appdata/gnome-power-statistics.appdata.xml.in
@@ -66,4 +66,5 @@
   </kudos>
   <url type="homepage">http://www.gnome.org/projects/gnome-power-manager/</url>
   <updatecontact>richard_at_hughsie.com</updatecontact>
+  <project_group>GNOME</project_group>
 </application>