Bump regex from 1.4.2 to 1.5.5 in /rust

Bumps [regex](https://github.com/rust-lang/regex) from 1.4.2 to 1.5.5.
- [Release notes](https://github.com/rust-lang/regex/releases)
- [Changelog](https://github.com/rust-lang/regex/blob/master/CHANGELOG.md)
- [Commits](rust-lang/regex@1.4.2...1.5.5)

---
updated-dependencies:
- dependency-name: regex
  dependency-type: direct:production
...

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Author: dependabot[bot]