Add two new-in-py3.13 class attributes to GroupBase

[inducer]

Fixes compatibility with Python 3.13.

Without this, errors such as this occur:

Traceback (most recent call last):
  File "/home/babybuddy/babybuddy/babybuddy/wsgi.py", line 9, in <module>
    application = get_wsgi_application()
  File "/home/babybuddy/babybuddy/.venv/lib/python3.13/site-packages/django/core/wsgi.py", line 12, in get_wsgi_application
    django.setup(set_prefix=False)
    ~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^
  File "/home/babybuddy/babybuddy/.venv/lib/python3.13/site-packages/django/__init__.py", line 24, in setup
    apps.populate(settings.INSTALLED_APPS)
    ~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/babybuddy/babybuddy/.venv/lib/python3.13/site-packages/django/apps/registry.py", line 116, in populate
    app_config.import_models()
    ~~~~~~~~~~~~~~~~~~~~~~~~^^
  File "/home/babybuddy/babybuddy/.venv/lib/python3.13/site-packages/django/apps/config.py", line 269, in import_models
    self.models_module = import_module(models_module_name)
                         ~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.13/importlib/__init__.py", line 88, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
           ~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/babybuddy/babybuddy/core/models.py", line 16, in <module>
    from babybuddy.site_settings import NapSettings
  File "/home/babybuddy/babybuddy/babybuddy/site_settings.py", line 20, in <module>
    class NapSettings(dbsettings.Group):
    ...<15 lines>...
        )
  File "/home/babybuddy/babybuddy/.venv/lib/python3.13/site-packages/dbsettings/group.py", line 22, in __init__
    raise TypeError('The type of %s (%s) is not a valid Value.' %
                    (attribute_name, attr.__class__.__name__))
TypeError: The type of __firstlineno__ (int) is not a valid Value.