Update dependency @openzeppelin/test-helpers to v0.5.16

[renovate[bot]]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
@openzeppelin/test-helpers	0.5.15 -> 0.5.16

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Release Notes

OpenZeppelin/openzeppelin-test-helpers

### [`v0.5.16`](https://togithub.com/OpenZeppelin/openzeppelin-test-helpers/blob/HEAD/CHANGELOG.md#​0516-2022-09-06) [Compare Source](https://togithub.com/OpenZeppelin/openzeppelin-test-helpers/compare/v0.5.15...v0.5.16) - Fix warning under Hardhat 2.11.

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