Update log requirement to 0.4
Update log requirement to 0.4

Updates the requirements on [log](https://github.com/rust-lang/log) to permit the latest version.
- [Release notes](https://github.com/rust-lang/log/releases)
- [Changelog](https://github.com/rust-lang-nursery/log/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rust-lang/log/commits/env_logger-0.4.3)

Signed-off-by: dependabot[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@dependabot.com>
michiel/xflow-rust,gears-project/gears-core-rust,gears-project/gears-core-rust,michiel/xflow-rust,michiel/xflow-rust,gears-project/gears-core-rust