Update dependency sinon to v8.1.1

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
sinon (source)	devDependencies	patch	8.1.0 -> 8.1.1

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Release Notes

sinonjs/sinon

### [`v8.1.1`](https://togithub.com/sinonjs/sinon/blob/master/CHANGELOG.md#​811--2020-01-22) [Compare Source](https://togithub.com/sinonjs/sinon/compare/v8.1.0...v8.1.1) ================== - Fundraiser for better docs:

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