Update dependency sinon to v9

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
sinon (source)	devDependencies	major	8.1.1 -> 9.0.0

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Release Notes

sinonjs/sinon

### [`v9.0.0`](https://togithub.com/sinonjs/sinon/blob/master/CHANGELOG.md#​900--2020-02-19) [Compare Source](https://togithub.com/sinonjs/sinon/compare/v8.1.1...v9.0.0) ================== - Ignore errors on thisValue property accesses ([#​2216](https://togithub.com/sinonjs/sinon/issues/2216)) - Add firstArg to spy calls and fakes. ([#​2150](https://togithub.com/sinonjs/sinon/issues/2150)) - Drop Node 8 support

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