doc: split process.umask() entry into two

Split doc entries for process.umask() into one entry for process.umask()
(which is deprecated) and another for `process.umask(mask)` which is
not deprecated.

Backport-PR-URL: https://github.com/nodejs/node/pull/34591
PR-URL: https://github.com/nodejs/node/pull/32711


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>