Bump log from 0.4.19 to 0.4.20

Bumps [log](https://github.com/rust-lang/log) from 0.4.19 to 0.4.20.
- [Release notes](https://github.com/rust-lang/log/releases)
- [Changelog](https://github.com/rust-lang/log/blob/master/CHANGELOG.md)
- [Commits](rust-lang/log@0.4.19...0.4.20)

---
updated-dependencies:
- dependency-name: log
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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