test: refactor test-esm-namespace.mjs

Remove unused `name` argument that is different from a subsequent `name`
argument in a different but nearby function. This was mildly confusing
to me at first, so hopefully this change clarifies things for others
reading the test.

PR-URL: https://github.com/nodejs/node/pull/25117


Reviewed-By: James M Snell <jasnell@gmail.com>