qom: Fix typo in Object's documentation

Fixes a warning from gtk-doc.
Signed-off-by: NAndreas Färber <afaerber@suse.de>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>

include/qemu/object.h

@@ -330,7 +330,7 @@ struct TypeInfo
 
 /**
  * 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.