app: Document when floating variants are consumed

Bug #700203.

gio/gaction.c

@@ -374,6 +374,8 @@ g_action_get_enabled (GAction *action)
  * the parameter type given at construction time).  If the parameter
  * type was %NULL then @parameter must also be %NULL.
  *
+ * If the @parameter GVariant is floating, it is consumed.
+ *
  * Since: 2.28
  **/
 void

gio/gsimpleaction.c

@@ -144,6 +144,8 @@ g_simple_action_change_state (GAction  *action,
  * property.  Instead, they should call g_action_change_state() to
  * request the change.
  *
+ * If the @value GVariant is floating, it is consumed.
+ *
  * Since: 2.30
  **/
 void