gh-98240: Updated Path.rename docs, when it is atomic (GH-98245)

(cherry picked from commit 0023f51)

Co-authored-by: Mateusz <mateka@users.noreply.github.com>

Author: miss-islington

Doc/library/pathlib.rst

@@ -1068,6 +1068,8 @@ call fails (for example because the path doesn't exist).
    relative to the current working directory, *not* the directory of the Path
    object.
 
+   It is implemented in terms of :func:`os.rename` and gives the same guarantees.
+
    .. versionchanged:: 3.8
       Added return value, return the new Path instance.