console: use 'label' argument for time and timeEnd

Turns out the argument is actually called label in the console spec,
while being wrongly named on MDN. This reverts commit
8c043c12.

MDN has been updated in:

https://developer.mozilla.org/en-US/docs/Web/API/Console/timeEnd$compare?locale=en-US&to=947893&from=918571
https://developer.mozilla.org/en-US/docs/Web/API/Console/time$compare?locale=en-US&to=947891&from=896987

PR-URL: https://github.com/nodejs/node/pull/3590


Reviewed-By: targos - Michaël Zasso <mic.besace@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>