Update dependency motor to v3.1.2

[renovate[bot]]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
motor	==3.1.1 -> ==3.1.2

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Release Notes

mongodb/motor

### [`v3.1.2`](https://togithub.com/mongodb/motor/releases/tag/3.1.2) [Compare Source](https://togithub.com/mongodb/motor/compare/3.1.1...3.1.2) Release notes: https://www.mongodb.com/community/forums/t/motor-3-1-2-released/220552

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