Log Message:
py-magic-wormhole: update to 0.13.0.

## Release 0.13.0 (10-Aug-2023)

* Python 2.7 support is dropped (#457)
* Python 3.5 and 3.6 are past their EOL date and support is dropped (#448)
* SECURITY: Replace "weird" characters in receiver's display (#476)
* SECURITY: all past binary signatures are now in Git
* Use the HKDF primitive from "cryptography" (#462)
* `wormhole receive` now accepts `--allocate-code` so that a sender can
  use `--code` to send them a file (#450)
* Stream to disk after 10MB on directory receive (#447)
* Handle SSH keys with comments properly (#434)
* Properly parse IPv6 Transit address (#461)

Also of interest to developers in this release are a few changes
to the experimental Dilation implementation and description; some
documentation cleanups; dropping of dependencies; and some test
cleanups.  The Dilation changes properly send `use-version` and
split messages over Noise-sized chunks more seamlessly (allowing
the specified 4-byte maximum message size at the application layer).