fix typo

Summary:
properties that has been set before -> properties that have been set before
Closes https://github.com/facebook/react-native/pull/15370

Differential Revision: D5563802

Pulled By: hramos

fbshipit-source-id: 288032555308a7e89ac365ff091b01ca381d4c80

docs/NativeComponentsAndroid.md

@@ -67,7 +67,7 @@ Except from `name`, `@ReactProp` annotation may take following optional argument
 
 Setter declaration requirements for methods annotated with `@ReactPropGroup` are different than for `@ReactProp`, please refer to the `@ReactPropGroup` annotation class docs for more information about it.
 
-**IMPORTANT!** in ReactJS updating the property value will result in setter method call. Note that one of the ways we can update component is by removing properties that has been set before. In that case setter method will be called as well to notify view manager that property has changed. In that case "default" value will be provided (for primitive types "default" can value can be specified using `defaultBoolean`, `defaultFloat`, etc. arguments of `@ReactProp` annotation, for complex types setter will be called with value set to `null`).
+**IMPORTANT!** in ReactJS updating the property value will result in setter method call. Note that one of the ways we can update component is by removing properties that have been set before. In that case setter method will be called as well to notify view manager that property has changed. In that case "default" value will be provided (for primitive types "default" can value can be specified using `defaultBoolean`, `defaultFloat`, etc. arguments of `@ReactProp` annotation, for complex types setter will be called with value set to `null`).
 
 ```java
   @ReactProp(name = "src")