[fix] "Object prototype may only be an Object or null: undefined" from supertest in browser contexts

## Describe the bug

**Node.js version:** 20.10.0

**OS version:** debian trixie/sid

**Description:** Including supertest in a cypress project results in the error `Object prototype may only be an Object or null: undefined` when supertest tries to include superagent.

## Actual behavior

Creating a blank cypress project and including supertest as a requirement in any spec file generates the error
```
Object prototype may only be an Object or null: undefined
```
With the backtrace:

```
at Function.setPrototypeOf ()
at ./node_modules/supertest/lib/agent.js (webpack://cypress-supertest-issue-minimal/./node_modules/supertest/lib/agent.js:36:0)
at __webpack_require__ (webpack://cypress-supertest-issue-minimal/webpack/bootstrap:19:0)
at ./node_modules/supertest/index.js (webpack://cypress-supertest-issue-minimal/./node_modules/supertest/index.js:9:14)
at __webpack_require__ (webpack://cypress-supertest-issue-minimal/webpack/bootstrap:19:0)
at eval (webpack://cypress-supertest-issue-minimal/./cypress/e2e/spec.cy.js:1:18)
```

## Expected behavior

It should be possible to require (and use) the library without issue, as was the case until version 6.2.4.

## Code to reproduce

I created an example project with a minimal reproduction here: https://github.com/codders/cypress-supertest-issue-minimal

## Checklist

- [x] I have searched through GitHub issues for similar issues.
- [x] I have completely read through the README and documentation.
- [x] I have tested my code with the latest version of Node.js and this package and confirmed it is still not working.