doc: fix minor grammar mistake in streams docs

PR-URL: #606
Reviewed-By: Rod Vagg <[email protected]>

Author: ttrfwork

doc/api/stream.markdown

@@ -1175,8 +1175,8 @@ as a result of this chunk.
 
 Call the callback function only when the current chunk is completely
 consumed.  Note that there may or may not be output as a result of any
-particular input chunk. If you supply as the second argument to the
-it will be passed to push method, in other words the following are
+particular input chunk. If you supply output as the second argument to the
+callback, it will be passed to push method, in other words the following are
 equivalent:
 
 ```javascript