test: remove string error from strictEqual

Removes the string error from the assertion call to improve the error
message shown on screen when the test fails.

PR-URL: https://github.com/nodejs/node/pull/21292


Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>