Update cryptography requirement from >=2.6,<39.0 to >=2.6,<40.0 (#878)

Update cryptography requirement from >=2.6,<39.0 to >=2.6,<40.0 (#878)

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...39.0.0)

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

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(cherry picked from commit 67809b4a4d69ae88ad1e6c77a21e9c7a4a081e03)