test: remove third argument from call to assert.strictEqual()

Remove the message argument from call to assert.strictEqual so
that the AssertionError will report the value of er.code, and add
a comment with the message.

PR-URL: https://github.com/nodejs/node/pull/19659


Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Tiancheng "Timothy" Gu <timothygu99@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>