doc: clearify that http does chunked encoding itself

Co-authored-by: Antoine du Hamel <duhamelantoine1995@gmail.com>

doc/api/http.md

@@ -1003,11 +1003,11 @@ added: v0.1.29
 * `callback` {Function}
 * Returns: {boolean}
 
-Sends a chunk of the body. By calling this method
-many times, a request body can be sent to a
-server. In that case, it is suggested to use the
-`['Transfer-Encoding', 'chunked']` header line when
-creating the request.
+Sends a chunk of the body. This method can be called multiple times. If no
+`Content-Length` is set, data will automatically be encoded in HTTP Chunked
+transfer encoding, so that server knows when the data ends. The
+`Transfer-Encoding: chunked` header is added. Calling [`request.end()`][]
+is necessary to finish sending the request.
 
 The `encoding` argument is optional and only applies when `chunk` is a string.
 Defaults to `'utf8'`.