doc: update write callback documentation

- replace _*may or may not* be called_ with _will be called_ because the
  callback is always called
- remove _To reliably detect write errors, add a listener for the
  `'error'` event_ because the `error` event will NOT be emitted if a
  write occurs after the stream has been closed

PR-URL: #38959
Fixes: #38704
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Robert Nagy <ronagy@icloud.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

doc/api/stream.md

@@ -627,9 +627,8 @@ changes:
 
 The `writable.write()` method writes some data to the stream, and calls the
 supplied `callback` once the data has been fully handled. If an error
-occurs, the `callback` *may or may not* be called with the error as its
-first argument. To reliably detect write errors, add a listener for the
-`'error'` event. The `callback` is called asynchronously and before `'error'` is
+occurs, the `callback` will be called with the error as its
+first argument. The `callback` is called asynchronously and before `'error'` is
 emitted.
 
 The return value is `true` if the internal buffer is less than the