doc: add missing word in Transform stream intro

doc/api/stream.markdown

@@ -1037,8 +1037,8 @@ connected in some way to the input, such as a [zlib][] stream or a
 There is no requirement that the output be the same size as the input,
 the same number of chunks, or arrive at the same time.  For example, a
 Hash stream will only ever have a single chunk of output which is
-provided when the input is ended.  A zlib stream will either produce
-much smaller or much larger than its input.
+provided when the input is ended.  A zlib stream will produce output
+that is either much smaller or much larger than its input.
 
 Rather than implement the [`_read()`][] and [`_write()`][] methods, Transform
 classes must implement the `_transform()` method, and may optionally