Change the Config object back to namedtuple.

It was one originally, then changed to a dataclass, but I have a
slight preference for it being a namedtuple, since it's meant to be
that sort of "struct" or "record" container type.

docs/usage.rst

@@ -257,7 +257,7 @@ Alternative configuration
 If you don't want to configure your Akismet client via the standard environment
 variables, or aren't able to set the environment variables, you can avoid the
 ``validated_client()`` method and instantiate your Akismet client
-directly. This is done via the :class:`akismet.Config` utility dataclass. You
+directly. This is done via the :class:`akismet.Config` utility tuple. You
 should also the make sure to validate the configuration before trying to use
 the client.
 

src/akismet/_common.py

@@ -4,7 +4,6 @@
 """
 # SPDX-License-Identifier: BSD-3-Clause
 
-import dataclasses
 import enum
 import os
 import sys
@@ -83,10 +82,10 @@ class CheckResponse(enum.IntEnum):
     DISCARD = 2
 
 
-@dataclasses.dataclass
-class Config:
+class Config(typing.NamedTuple):
     """
-    An Akismet configuration, consisting of a key and a URL.
+    A :func:`~collections.namedtuple` representing Akismet configuration, consisting
+    of a key and a URL.
 
     You only need to use this if you're manually configuring an Akismet API client
     (which should be rare) rather than letting the ``validated_client()`` constructor