doc: fix typo in stream.md

PR-URL: #14364
Fixes: #14362
Reviewed-By: Timothy Gu <timothygu99@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

doc/api/stream.md

@@ -1922,7 +1922,7 @@ user programs.
 
 `transform._transform()` is never called in  parallel; streams implement a
 queue mechanism, and to receive the next chunk, `callback` must be
-called, either synchronously or asychronously.
+called, either synchronously or asynchronously.
 
 #### Class: stream.PassThrough