removed v-bind.prop example since is wrong (vuejs#899)

* removed v-bind.prop example since is wrong

* Fix example to pass down parent props in common with a child component

Author: dotBits

src/v2/api/index.md

@@ -1785,9 +1785,9 @@ All lifecycle hooks automatically have their `this` context bound to the instanc
 
   <!-- prop binding. "prop" must be declared in my-component. -->
   <my-component :prop="someThing"></my-component>
-
+  
   <!-- pass down parent props in common with a child component -->
-  <child-component v-bind.prop="$props"></child-component>
+  <child-component v-bind="$props"></child-component>
 
   <!-- XLink -->
   <svg><a :xlink:special="foo"></a></svg>