Bump regex from 1.9.1 to 1.9.4

Bumps [regex](https://github.com/rust-lang/regex) from 1.9.1 to 1.9.4.
- [Release notes](https://github.com/rust-lang/regex/releases)
- [Changelog](https://github.com/rust-lang/regex/blob/master/CHANGELOG.md)
- [Commits](rust-lang/regex@1.9.1...1.9.4)

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

Signed-off-by: dependabot[bot] <[email protected]>