Update react monorepo to v16.12.0

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
react (source)	dependencies	minor	16.11.0 -> 16.12.0
react-dom (source)	dependencies	minor	16.11.0 -> 16.12.0

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Release Notes

facebook/react

### [`v16.12.0`](https://togithub.com/facebook/react/blob/master/CHANGELOG.md#​16120-November-14-2019) [Compare Source](https://togithub.com/facebook/react/compare/v16.11.0...v16.12.0) ##### React DOM - Fix passive effects (`useEffect`) not being fired in a multi-root app. ([@​acdlite](https://togithub.com/acdlite) in [#​17347](https://togithub.com/facebook/react/pull/17347)) ##### React Is - Fix `lazy` and `memo` types considered elements instead of components ([@​bvaughn](https://togithub.com/bvaughn) in [#​17278](https://togithub.com/facebook/react/pull/17278))

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