Update cryptography requirement from >=2.6,<38.0 to >=2.6,<39.0

Update cryptography requirement from >=2.6,<38.0 to >=2.6,<39.0

Updates the requirements on [cryptography](https://github.com/pyca/cryptography) to permit the latest version.
- [Release notes](https://github.com/pyca/cryptography/releases)
- [Changelog](https://github.com/pyca/cryptography/blob/main/CHANGELOG.rst)
- [Commits](https://github.com/pyca/cryptography/compare/2.6...38.0.1)

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

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