chore(deps): update dependency sinon to v8.1.0

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
sinon (source)	devDependencies	minor	8.0.4 -> 8.1.0

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Release Notes

sinonjs/sinon

### [`v8.1.0`](https://togithub.com/sinonjs/sinon/blob/master/CHANGELOG.md#​810--2020-01-16) [Compare Source](https://togithub.com/sinonjs/sinon/compare/v8.0.4...v8.1.0) ================== - Support negative indices in getCall ([#​2199](https://togithub.com/sinonjs/sinon/issues/2199))

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