test: replace should with node:assert

[jimmywarting]

Part of https://github.com/ladjs/superagent/issues/1779

Checklist

• [x] I have ensured my pull request is not behind the main or master branch of the original repository.
• [x] I have rebased all commits where necessary so that reviewing this pull request can be done without having to merge it first.
• [x] I have written a commit message that passes commitlint linting.
• [x] I have ensured that my code changes pass linting tests.
• [x] I have ensured that my code changes pass unit tests.
• [x] I have described my pull request and the reasons for code changes along with context if necessary.

[codecov-commenter]

Codecov Report

Patch and project coverage have no change.

Comparison is base (83e92cb) 94.39% compared to head (a679c6a) 94.39%. Report is 1 commits behind head on master.

:exclamation: Your organization is not using the GitHub App Integration. As a result you may experience degraded service beginning May 15th. Please install the Github App Integration for your organization. Read more.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #1782 +/- ## ======================================= Coverage 94.39% 94.39% ======================================= Files 14 14 Lines 1141 1141 ======================================= Hits 1077 1077 Misses 64 64 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.

[titanism]

So clean 🧼 !