Update Typo in readme

Author: mrsimonbennett

README.md

@@ -609,7 +609,7 @@ data until the buffer drains.
 The stream SHOULD send a `drain` event once the buffer is ready to accept
 more data.
 
-Similarly, if the the stream is not writable (already in a closed state)
+Similarly, if the stream is not writable (already in a closed state)
 it MUST NOT process the given `$data` and SHOULD return `false`,
 indicating that the caller should stop sending data.