view iface: remove manager property

There's no reason at all why manager should be a property inside the
views. It won't benefit of bindings or anything else inherent to GObject
property system.

src/gcal-view.c

@@ -39,14 +39,6 @@ gcal_view_base_init (gpointer g_iface)
                               ICAL_TIME_TYPE,
                               G_PARAM_READWRITE));
 
-      g_object_interface_install_property (
-          g_iface,
-          g_param_spec_pointer ("manager",
-                                "The manager object",
-                                "A weak reference to the app manager object",
-                                G_PARAM_CONSTRUCT_ONLY |
-                                G_PARAM_READWRITE));
-
       g_signal_new ("create-event",
                     GCAL_TYPE_VIEW,
                     G_SIGNAL_RUN_LAST,