normalizeProps 删除多余条件

与源码同步，此条件多余！

docs/art/4vue-normalize.md

@@ -346,7 +346,7 @@ function normalizeProps (options: Object, vm: ?Component) {
         ? val
         : { type: val }
     }
-  } else if (process.env.NODE_ENV !== 'production' && props) {
+  } else if (process.env.NODE_ENV !== 'production') {
     warn(
       `Invalid value for option "props": expected an Array or an Object, ` +
       `but got ${toRawType(props)}.`,