doc: update stream.pipeline() signature

The  `...transforms` parameter is optional.

Refs: https://github.com/nodejs/node/blob/0875837417/lib/internal/streams/pipeline.js#L130-L132
Refs: https://github.com/nodejs/node/blob/e559842188/doc/api/stream.md#streams-compatibility-with-async-generators-and-async-iterators

PR-URL: #31789
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Robert Nagy <ronagy@icloud.com>
Reviewed-By: Yongsheng Zhang <zyszys98@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

doc/api/stream.md

@@ -1555,7 +1555,7 @@ const cleanup = finished(rs, (err) => {
 });
 ```
 
-### `stream.pipeline(source, ...transforms, destination, callback)`
+### `stream.pipeline(source[, ...transforms], destination, callback)`
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