Make the changelog entry more verbose

Co-authored-by: NTzu-ping Chung <uranusjr@gmail.com>

news/4256.removal.rst

-``freeze`` no longer excludes the ``setuptools``, ``distribute`` and ``wheel``
-packages from the output by default when running on Python 3.12 or later.
-Use ``--exclude`` if you wish to exclude any of these packages.
+``freeze`` no longer excludes the ``setuptools``, ``distribute``, and ``wheel``
+from the output when running on Python 3.12 or later, where they are not
+included in a virtual environment by default. Use ``--exclude`` if you wish to
+exclude any of these packages.