The cryptography dependency has been removed in favor of the version

bound to cryptozoology, which is now a dependency of Djblets 7.

Keeping the cryptography dependency version in one place helps to

avoid version conflicts between the various modules.
We'll be bumping the cryptozoology dependency when needed to get new

major cryptography changes.

Built new environments with the Djblets and Review Board changes.

Verified that I had the expected versions of these dependencies.