Bump cryptography from 2.1.4 to 3.4.6

Bumps cryptography from 2.1.4 to 3.4.6.

Changelog

Sourced from cryptography's changelog.

3.4.6 - 2021-02-16

* Updated Windows, macOS, and ``manylinux`` wheels to be compiled with
  OpenSSL 1.1.1j.

.. _v3-4-5:

3.4.5 - 2021-02-13

• Various improvements to type hints.
• Lower the minimum supported Rust version (MSRV) to >=1.41.0. This change improves compatibility with system-provided Rust on several Linux distributions.
• cryptography will be switching to a new versioning scheme with its next feature release. More information is available in our :doc:/api-stability documentation.

.. _v3-4-4:

3.4.4 - 2021-02-09

* Added a ``py.typed`` file so that ``mypy`` will know to use our type
  annotations.
* Fixed an import cycle that could be triggered by certain import sequences.

.. _v3-4-3:

3.4.3 - 2021-02-08

• Specify our supported Rust version (>=1.45.0) in our setup.py so users on older versions will get a clear error message.

.. _v3-4-2:

3.4.2 - 2021-02-08

* Improvements to make the rust transition a bit easier. This includes some
  better error messages and small dependency fixes. If you experience
  installation problems **Be sure to update pip** first, then check the
  :doc:`FAQ </faq>`.

.. _v3-4-1:

3.4.1 - 2021-02-07

... (truncated)

Commits

• 75b002a Release 346 (#5840)
• 4d77fb9 3.4.5 backports and changelog/version bump (#5827)
• 4a3018e 3.4.4 - backports, changelog, and version bumps (#5803)
• 86c9e4a version bump, changelog already done (#5791)
• 0f40cb3 [3.4] Specify an MSRV in setup.py (#5789) (#5790)
• 74a3df4 3.4.2 changelog and version bump (#5784)
• 4a66e2b [3.4] More aggressively point people at Rust version docs (#5782) (#5783)
• 843ada6 Remove setuptools_rust from install requirement (#5779) (#5781)
• e5b5c3d Interface: Make annotation check optional (#5775) (#5780)
• ebde3be 3.4.1 fixes and changelog bump (#5761)
• Additional commits viewable in compare view