doc: unify optional arguments format in headings

Make space and comma distribution in some headings
consistent with the majority of headings.

PR-URL: https://github.com/nodejs/node/pull/22397


Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>