chore(mongodb): bump mongodb/mongodbatlas in /providers/mongodb

Bumps [mongodb/mongodbatlas](https://github.com/mongodb/terraform-provider-mongodbatlas) from 2.10.0 to 2.12.0.
- [Release notes](https://github.com/mongodb/terraform-provider-mongodbatlas/releases)
- [Changelog](https://github.com/mongodb/terraform-provider-mongodbatlas/blob/master/CHANGELOG.md)
- [Commits](mongodb/terraform-provider-mongodbatlas@v2.10.0...v2.12.0)

---
updated-dependencies:
- dependency-name: mongodb/mongodbatlas
  dependency-version: 2.12.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]