build(deps): bump regex from 1.5.4 to 1.5.6 in /rust (#65)

Bumps [regex](https://github.com/rust-lang/regex) from 1.5.4 to 1.5.6.
- [Release notes](https://github.com/rust-lang/regex/releases)
- [Changelog](https://github.com/rust-lang/regex/blob/master/CHANGELOG.md)
- [Commits](rust-lang/regex@1.5.4...1.5.6)

---
updated-dependencies:
- dependency-name: regex
  dependency-type: indirect
...

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Author: dependabot[bot]