stream: fix off-by-factor-16 error in comment
stream: fix off-by-factor-16 error in comment

The high watermark is capped at 8 MB, not 128 MB like the comment
in lib/_stream_readable.js said.

PR-URL: https://github.com/nodejs/node/pull/2479
Reviewed-By: Chris Dickinson <38a75c4c4f5646d63b752460df745c5b937b7e58@gmail.com>
Reviewed-By: Sakthipriyan Vairamani <b84950071fc99921a72f4fa56f6cad2496b3223c@gmail.com>

dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node