Update dependency sinon to v8

[renovate-bot]

This PR contains the following updates:

Package	Type	Update	Change
sinon (source)	devDependencies	major	^7.2.7 -> ^8.0.0

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Release Notes

sinonjs/sinon

v8.0.4

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• Remove misleading 'own' from exception message

v8.0.3

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• Move .printf to proxy

v8.0.2

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• Upgrade @​sinonjs/samsam to latest
• Upgrade nise to 3.0.1

v8.0.1

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• Force upgrade @​sinonjs/commons (#​2181)
• Update docs/changelog.md and set new release id in docs/_config.yml
• Add release documentation for v8.0.0

v8.0.0

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The major release is caused by removing old mistakes and upgrading dependencies that themselves have had new major releases.

• Upgrade nise, @​sinonjs/formatio, @​sinonjs/samsam and @​sinonjs/referee
• Update lolex and nise to get new async timer methods (see https://github.com/sinonjs/lolex/blob/master/CHANGELOG.md)
• Remove sinon.spyCall
• Remove sinon.sandbox.create
• Remove obsolete deprecated.printWarning stubbing from test

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[kurtisvg]

/cloudsql LGTM

[ace-n]

functions/pubsub is failing due to timeout - maybe it needs to be re-run?

@fhinkel feel free to fix it (or ping me) if it's a consistent failure.