Fix minor docstring issues in `dataclasses.py`. (gh-93024) (GH-95286)

Previously, when using `functools.wrap` around them (and inherit their docstrings), sphinx renders the docstrings badly and raises warnings about wrong indent.
(cherry picked from commit b8c528694edb7a31020116956cc4daf07a5cd97f)

Co-authored-by: Roman Novak <44512421+romanngg@users.noreply.github.com>