Update "Migrating to GDBus" chapter to take gdbus-codegen(1) into account

Signed-off-by: David Zeuthen <davidz@redhat.com>

gio/tests/gdbus-example-objectmanager.xml

@@ -1,24 +1,28 @@
 <node>
-
   <!-- org.gtk.GDBus.Example.ObjectManager.Animal:
-       @short_description: Simple Animal
+       @short_description: Example docs generated by gdbus-codegen(1)
 
-       This interface is used to describe a simple animal.
+       This D-Bus interface is used to describe a simple animal.
     -->
   <interface name="org.gtk.GDBus.Example.ObjectManager.Animal">
-
     <!-- Mood: The mood of the animal.
 
          Known values for this property include
          <literal>Happy</literal> and <literal>Sad</literal>. Use the
          org.gtk.GDBus.Example.ObjectManager.Animal.Poke() method to
-         change this property -->
+         change this property.
+
+         This property influences how often the animal jumps up and
+         down, see the
+         #org.gtk.GDBus.Example.ObjectManager.Animal::Jumped signal
+         for more details.
+    -->
     <property name="Mood" type="s" access="read"/>
 
     <!--
         Poke:
         @make_sad: Whether to make the animal sad.
-        @make_angry: Whether to make the animal angry.
+        @make_happy: Whether to make the animal happy.
 
         Method used to changing the mood of the animal. See also the
         #org.gtk.GDBus.Example.ObjectManager.Animal:Mood property.
@@ -28,6 +32,14 @@
       <arg direction="in" type="b" name="make_happy"/>
     </method>
 
-  </interface>
+    <!--
+        Jumped:
+        @height: Height, in meters, that the animal jumped.
 
+        Emitted when the animal decides to jump.
+      -->
+    <signal name="Jumped">
+      <arg type="d" name="height"/>
+    </signal>
+  </interface>
 </node>