chore(deps): update prettier to v1.19.0

[renovate[bot]]

This PR contains the following updates:

Package	Update	Type	Change	Sourcegraph
prettier (source)	minor	devDependencies	1.18.2 -> 1.19.0

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Release Notes

prettier/prettier

### [`v1.19.0`](https://togithub.com/prettier/prettier/blob/master/CHANGELOG.md#​1190) [Compare Source](https://togithub.com/prettier/prettier/compare/1.18.2...1.19.0) [diff](https://togithub.com/prettier/prettier/compare/1.18.2...1.19.0) 🔗 [Release Notes](https://prettier.io/blog/2019/11/09/1.19.0.html)

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