[orca] Remove duplicate event listener registrations

[Joanmarie Diggs <joanied src gnome org>]

commit da2b7b49da076b3488be4707eca50da6223d62a3
Author: Joanmarie Diggs <jdiggs igalia com>
Date:   Thu Apr 2 18:01:20 2020 -0400

    Remove duplicate event listener registrations

 src/orca/event_manager.py | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)
---
diff --git a/src/orca/event_manager.py b/src/orca/event_manager.py
index 52ec7e0d4..6f4e80da4 100644
--- a/src/orca/event_manager.py
+++ b/src/orca/event_manager.py
@@ -65,13 +65,9 @@ class EventManager:
         debug.println(debug.LEVEL_INFO, 'Event manager initialized', True)
 
     def activate(self):
-        """Called when this presentation manager is activated."""
+        """Called when this event manager is activated."""
 
         debug.println(debug.LEVEL_INFO, 'EVENT MANAGER: Activating', True)
-        self._registerListener("window:activate")
-        self._registerListener("window:deactivate")
-        self._registerListener("object:children-changed")
-        self._registerListener("mouse:button")
         self.registerKeystrokeListener(self._processKeyboardEvent)
         self._active = True
         debug.println(debug.LEVEL_INFO, 'EVENT MANAGER: Activated', True)