test: remove undefined function

`common.fail()` no longer exists as its functionality is now in
`assert.fail()`. Replace only two instances in the code base with
`assert.fail()`.

PR-URL: https://github.com/nodejs/node/pull/17845


Reviewed-By: Timothy Gu <timothygu99@gmail.com>
Reviewed-By: Anatoli Papirovski <apapirovski@mac.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Weijia Wang <starkwang@126.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Yuta Hiroto <hello@about-hiroppy.com>