Fix typo in create-subscription readme

PR: facebook#12473

packages/create-subscription/README.md

@@ -147,7 +147,7 @@ Below is an example showing how `create-subscription` can be used with native Pr
 
 **Note** that it an initial render value of `undefined` is unavoidable due to the fact that Promises provide no way to synchronously read their current value.
 
-**Note** the lack of a way to "unsubscribe" from a Promise can result in memory leaks as long as something has a reference to the Promise. This should be taken into considerationg when determining whether Promises are appropriate to use in this way within your application.
+**Note** the lack of a way to "unsubscribe" from a Promise can result in memory leaks as long as something has a reference to the Promise. This should be taken into consideration when determining whether Promises are appropriate to use in this way within your application.
 
 ```js
 import React from "react";