doc: clarify windows specific behaviour

It was not possible to understand which, if either, of the sentences
after the first ("Windows does not... emulation") apply specifically to
Windows.  Specifically, `kill(pid, 0)` works on Linux and Windows and I
couldn't find it documented anywhere else, but the unconditional
termination occurs only on Windows.

PR-URL: https://github.com/nodejs/node/pull/32079


Reviewed-By: Bartosz Sosnowski <bartosz@janeasystems.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>