rust/checksum(deps): bump regex in /tools/checksum_updater (#522)

Bumps [regex](https://github.com/rust-lang/regex) from 1.12.3 to 1.12.4.
- [Release notes](https://github.com/rust-lang/regex/releases)
- [Changelog](https://github.com/rust-lang/regex/blob/master/CHANGELOG.md)
- [Commits](rust-lang/regex@1.12.3...1.12.4)

---
updated-dependencies:
- dependency-name: regex
  dependency-version: 1.12.4
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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Author: dependabot[bot]