Silently ignore pkg_resources override on 3.12+

This customization is generally provided by the distributor, and the
user can do nothing if the environment is configured incorrectly. So
instead of breaking pip entirely, we silently ignore the customization
and let the distributor correct the situation.

src/pip/_internal/metadata/__init__.py

@@ -4,7 +4,6 @@
 import sys
 from typing import TYPE_CHECKING, List, Optional, Type, cast
 
-from pip._internal.exceptions import PipError
 from pip._internal.utils.misc import strtobool
 
 from .base import BaseDistribution, BaseEnvironment, FilesystemWheel, MemoryWheel, Wheel
@@ -31,7 +30,8 @@ def _should_use_importlib_metadata() -> bool:
     """Whether to use the ``importlib.metadata`` or ``pkg_resources`` backend.
 
     By default, pip uses ``importlib.metadata`` on Python 3.11+, and
-    ``pkg_resourcess`` otherwise. This can be overridden by a couple of ways:
+    ``pkg_resources`` otherwise. On Python versions prior to 3.12, this can be
+    overridden by a couple of ways for transitional purposes:
 
     * If environment variable ``_PIP_USE_IMPORTLIB_METADATA`` is set, it
       dictates whether ``importlib.metadata`` is used, regardless of Python
@@ -41,6 +41,8 @@ def _should_use_importlib_metadata() -> bool:
       makes pip use ``pkg_resources`` (unless the user set the aforementioned
       environment variable to *True*).
     """
+    if sys.version_info >= (3, 12):
+        return True
     with contextlib.suppress(KeyError, ValueError):
         return bool(strtobool(os.environ["_PIP_USE_IMPORTLIB_METADATA"]))
     if sys.version_info < (3, 11):
@@ -62,10 +64,6 @@ def select_backend() -> Backend:
 
         return cast(Backend, importlib)
 
-    if sys.version_info >= (3, 12):
-        message = "Cannot use pkg_resources as metadata backend on Python 3.12+"
-        raise PipError(message)
-
     from . import pkg_resources
 
     return cast(Backend, pkg_resources)