mitmproxy: Update to 8.1.1

pkgsrc changes:
- Follow upstream requirements for py-cryptography (previously a workaround was
  added in order to avoid possible too new py-cryptography that was not yet
  present in pkgsrc)

Changes:
8.1.1
-----
* Support specifying the local address for outgoing connections
* Fix a bug where an excess empty chunk has been sent for chunked HEAD request.
* Drop pkg_resources dependency.
* Fix huge (>65kb) http2 responses corrupted.
* Remove overambitious assertions in the HTTP state machine,
  fix some error handling.

(leot)