`constants_from_enum` does not work for `StrEnum`

[dominikroblek]

constants_from_enum does not work for StrEnum.

Here is an example of an error caused by this bug:

Traceback (most recent call last):
  ...
    gin.constants_from_enum(Language)
  File "/workspace/finch/.venv/lib/python3.11/site-packages/gin/config.py", line 2798, in constants_from_enum
    return decorator(cls)
           ^^^^^^^^^^^^^^
  File "/workspace/finch/.venv/lib/python3.11/site-packages/gin/config.py", line 2793, in decorator
    constant('{}.{}'.format(module, str(value)), value)
  File "/workspace/finch/.venv/lib/python3.11/site-packages/gin/config.py", line 2756, in constant
    raise ValueError("Invalid constant selector '{}'.".format(name))
ValueError: Invalid constant selector 'pipecat.transcriptions.language.af-ZA'.