chore(deps): update dependency supertest to v4

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change	References
supertest	devDependencies	major	^3.0.0 -> ^4.0.0	source

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Release Notes

visionmedia/supertest

### [`v4.0.0`](https://togithub.com/visionmedia/supertest/releases/v4.0.0) [Compare Source](https://togithub.com/visionmedia/supertest/compare/v3.4.2...v4.0.0) - Merge pull request [#​539](https://togithub.com/visionmedia/supertest/issues/539) from ozzywalsh/fix-agent-defaults [`abf6bc3`](https://togithub.com/visionmedia/supertest/commit/abf6bc3) - Merge pull request [#​554](https://togithub.com/visionmedia/supertest/issues/554) from visionmedia/use-trust-localhost [`5914936`](https://togithub.com/visionmedia/supertest/commit/5914936)

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