qom: Fix typo in Object's documentation

Fixes a warning from gtk-doc.

Signed-off-by: Andreas Färber <afaerber@suse.de>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
diff --git a/include/qemu/object.h b/include/qemu/object.h
index 69cc2ab..c871254 100644
--- a/include/qemu/object.h
+++ b/include/qemu/object.h
@@ -330,7 +330,7 @@
 
 /**
  * OBJECT_CLASS:
- * @class: A derivative of #ObjectClas.
+ * @class: A derivative of #ObjectClass.
  *
  * Converts a class to an #ObjectClass.  Since all objects are #Objects,
  * this function will always succeed.