doc: make options of readableStream.pipeTo as optional

Refs: https://github.com/nodejs/node/blob/main/lib/internal/webstreams/readablestream.js#L380
PR-URL: #46180
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

doc/api/webstreams.md

@@ -273,7 +273,7 @@ const transformedStream = stream.pipeThrough(transform);
 })();
 ```
 
-#### `readableStream.pipeTo(destination, options)`
+#### `readableStream.pipeTo(destination[, options])`
 
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