Bump itoa from 1.0.17 to 1.0.18 in /src/_bcrypt (#1180)

Bumps [itoa](https://github.com/dtolnay/itoa) from 1.0.17 to 1.0.18.
- [Release notes](https://github.com/dtolnay/itoa/releases)
- [Commits](dtolnay/itoa@1.0.17...1.0.18)

---
updated-dependencies:
- dependency-name: itoa
  dependency-version: 1.0.18
  dependency-type: indirect
  update-type: version-update:semver-patch
...

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Author: dependabot[bot]