chore(deps): bump mongodb from 2.8.2 to 3.1.1

Bumps [mongodb](https://github.com/mongodb/mongo-rust-driver) from 2.8.2 to 3.1.1.
- [Release notes](https://github.com/mongodb/mongo-rust-driver/releases)
- [Commits](mongodb/mongo-rust-driver@v2.8.2...v3.1.1)

---
updated-dependencies:
- dependency-name: mongodb
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]