[gnome-system-monitor] Add `Activity` keyword to .desktop file

[Robert Roth <robertroth src gnome org>]

commit be1c7ac19727619f076d7193fe3c730762626d79
Author: Daniel Aleksandersen <code daniel priv no>
Date:   Mon Apr 3 17:09:47 2017 +0200

    Add `Activity` keyword to .desktop file
    
    For users used to macOS’ `Activity Monitor`.

 gnome-system-monitor.desktop.in.in |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/gnome-system-monitor.desktop.in.in b/gnome-system-monitor.desktop.in.in
index 9807090..3e8e85b 100644
--- a/gnome-system-monitor.desktop.in.in
+++ b/gnome-system-monitor.desktop.in.in
@@ -13,4 +13,4 @@ X-GNOME-Bugzilla-Bugzilla=GNOME
 X-GNOME-Bugzilla-Product=system-monitor
 X-GNOME-Bugzilla-Component=general
 X-GNOME-Bugzilla-Version=@VERSION@
-_Keywords=Monitor;System;Process;CPU;Memory;Network;History;Usage;Performance;Task;Manager;
+_Keywords=Monitor;System;Process;CPU;Memory;Network;History;Usage;Performance;Task;Manager;Activity