Bumps [downcast-rs](https://github.com/marcianx/downcast-rs) from 1.1.1 to 1.2.0.
- [Release notes](https://github.com/marcianx/downcast-rs/releases)
- [Changelog](https://github.com/marcianx/downcast-rs/blob/master/CHANGELOG.md)
- [Commits](marcianx/downcast-rs@v1.1.1...v1.2.0)

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