doc: correct vcbuild options for windows testing

Corrected parameter for running tests on Windows. Without the corrected
parameters, Windows users encounter an error about failing to sign the
build, "Failed to sign exe", which can be discouraging to new Windows
community members.

PR-URL: https://github.com/nodejs/node/pull/10686


Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Bartosz Sosnowski <bartosz@janeasystems.com>