converters/py-zfec: Update to 1.5.7.4

packaging changes: none (3.7 is not in pkgsrc)

* Release 1.5.7.4 (2023-10-23)

** Python 3.7 is no longer supported.
** Python 3.12 is now supported.
** Binary packages for the macOS "universal2" and "arm64" architectures are now provided.
** The benchmark tool has been ported to Python 3.
** The GIL is now released for zfec.Encoder and zfec.Decoder initialization and for encode and decode operations.
  This enables multithreaded use of zfec to use multiple CPU cores for increased aggregate throughput.

(gdt)