process: simplify check in previousValueIsValid()

This commit replaces a call to Number.isFinite() with a
cheaper typeof check. The subsequent range checks ensure that
the checked value is finite.

PR-URL: https://github.com/nodejs/node/pull/24836


Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Michaël Zasso <targos@protonmail.com>