[gnome-calculator] AppData: Mark as unremovable in GNOME Software

[Richard Hughes <rhughes src gnome org>]

commit a2272fa20404a2e1d9c8b97d5637ed60f8ad02a6
Author: Richard Hughes <richard hughsie com>
Date:   Mon Mar 28 16:30:31 2016 +0100

    AppData: Mark as unremovable in GNOME Software

 data/gnome-calculator.appdata.xml.in |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/data/gnome-calculator.appdata.xml.in b/data/gnome-calculator.appdata.xml.in
index 91fa706..cc381cb 100644
--- a/data/gnome-calculator.appdata.xml.in
+++ b/data/gnome-calculator.appdata.xml.in
@@ -50,6 +50,7 @@
   <url type="homepage">https://wiki.gnome.org/Apps/Calculator</url>
   <update_contact>mcatanzaro_at_gnome.org</update_contact>
   <project_group>GNOME</project_group>
+  <compulsory_for_desktop>GNOME</compulsory_for_desktop>
   <kudos>
     <kudo>AppMenu</kudo>
     <kudo>HiDpiIcon</kudo>