fix(deps): update dependency @google-cloud/firestore to ^4.12.2

[renovate[bot]]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
@google-cloud/firestore	^4.12.0 -> ^4.12.2

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Release Notes

googleapis/nodejs-firestore

### [`v4.12.2`](https://togithub.com/googleapis/nodejs-firestore/blob/master/CHANGELOG.md#​4122-httpswwwgithubcomgoogleapisnodejs-firestorecomparev4121v4122-2021-05-27) [Compare Source](https://togithub.com/googleapis/nodejs-firestore/compare/v4.12.1...v4.12.2) ### [`v4.12.1`](https://togithub.com/googleapis/nodejs-firestore/blob/master/CHANGELOG.md#​4121-httpswwwgithubcomgoogleapisnodejs-firestorecomparev4120v4121-2021-05-27) [Compare Source](https://togithub.com/googleapis/nodejs-firestore/compare/v4.12.0...v4.12.1)

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