Update dependency supertest to v6.1.6

[mend-for-github-com[bot]]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
supertest	6.1.3 -> 6.1.6

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Release Notes

visionmedia/supertest

### [`v6.1.6`](https://togithub.com/visionmedia/supertest/releases/v6.1.6) [Compare Source](https://togithub.com/visionmedia/supertest/compare/v6.1.5...v6.1.6) - Merge pull request [#​735](https://togithub.com/visionmedia/supertest/issues/735) from benjosantony/master [`28116f9`](https://togithub.com/visionmedia/supertest/commit/28116f9) - Add on to the mitigation in [https://github.com/visionmedia/supertest/pull/728](https://togithub.com/visionmedia/supertest/pull/728)/commits to support empty array response body [`ed0f68d`](https://togithub.com/visionmedia/supertest/commit/ed0f68d) ### [`v6.1.5`](https://togithub.com/visionmedia/supertest/releases/v6.1.5) [Compare Source](https://togithub.com/visionmedia/supertest/compare/v6.1.4...v6.1.5) - Merge pull request [#​728](https://togithub.com/visionmedia/supertest/issues/728) from swantzter/fix/array-of-statuses-body [`3c46dae`](https://togithub.com/visionmedia/supertest/commit/3c46dae) - Mitigate array-of-statuses' impact on JSON bodies [`5a6999a`](https://togithub.com/visionmedia/supertest/commit/5a6999a) ### [`v6.1.4`](https://togithub.com/visionmedia/supertest/releases/v6.1.4) [Compare Source](https://togithub.com/visionmedia/supertest/compare/v6.1.3...v6.1.4) - Merge pull request [#​715](https://togithub.com/visionmedia/supertest/issues/715) from juanvillegas/feature/allows-expect-to-take-an-array [`7e4645c`](https://togithub.com/visionmedia/supertest/commit/7e4645c) - Allows expect to accept an array of statuses [`ab252f3`](https://togithub.com/visionmedia/supertest/commit/ab252f3)

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