test: fix typo in common/index.js

All tests using enoughTestCpu checks are always having the checks come
back false due to a typo in common/index.js. Fix the typo.

PR-URL: https://github.com/nodejs/node/pull/31931


Reviewed-By: Denys Otrishko <shishugi@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Yongsheng Zhang <zyszys98@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>