Update react monorepo to v16.8.1

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change	References
react	dependencies	patch	16.8.0 -> 16.8.1	homepage, source
react-dom	dependencies	patch	16.8.0 -> 16.8.1	homepage, source
react-test-renderer	devDependencies	patch	16.8.0 -> 16.8.1	homepage, source

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Release Notes

facebook/react

### [`v16.8.1`](https://togithub.com/facebook/react/blob/master/CHANGELOG.md#​1681-February-6-2019) [Compare Source](https://togithub.com/facebook/react/compare/v16.8.0...v16.8.1) ##### React DOM and React Test Renderer - Fix a crash when used together with an older version of React. ([@​bvaughn](https://togithub.com/bvaughn) in [#​14770](https://togithub.com/facebook/react/pull/14770)) ##### React Test Utils - Fix a crash in Node environment. ([@​threepointone](https://togithub.com/threepointone) in [#​14768](https://togithub.com/facebook/react/pull/14768))

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