test: remove redundant common.mustCall

All calls verify the cb is called, thus using `common.mustCall` is
not required inside of this function.

PR-URL: https://github.com/nodejs/node/pull/26738


Reviewed-By: Gus Caplan <me@gus.host>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>