doc: fix EventEmitter#eventNames() example

Replace myErr with myEE in one place.
Fix the expected output to have the actual formatting.

PR-URL: https://github.com/nodejs/node/pull/6417


Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Brian White <mscdex@mscdex.net>