assert: fix `assert.fail()` stack

This makes sure the error message visible in the error stack created
when using `assert.fail()` without any arguments or the message set
to `undefined` or `null` as only argument.
That was masked before due to other changes.

PR-URL: https://github.com/nodejs/node/pull/27525


Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>