[3.9] bpo-40833: Clarify Path.rename doc-string regarding relative paths (GH-20554)

(cherry picked from commit f97e42ef4d97dee64f45ed65170a6e77c8e46fdf)

Co-authored-by: Ram Rachum <ram@rachum.com>
diff --git a/Lib/pathlib.py b/Lib/pathlib.py
index babc443..147be2f 100644
--- a/Lib/pathlib.py
+++ b/Lib/pathlib.py
@@ -1366,17 +1366,26 @@
 
     def rename(self, target):
         """
-        Rename this path to the given path,
-        and return a new Path instance pointing to the given path.
+        Rename this path to the target path.
+
+        The target path may be absolute or relative. Relative paths are
+        interpreted relative to the current working directory, *not* the
+        directory of the Path object.
+
+        Returns the new Path instance pointing to the target path.
         """
         self._accessor.rename(self, target)
         return self.__class__(target)
 
     def replace(self, target):
         """
-        Rename this path to the given path, clobbering the existing
-        destination if it exists, and return a new Path instance
-        pointing to the given path.
+        Rename this path to the target path, overwriting if that path exists.
+
+        The target path may be absolute or relative. Relative paths are
+        interpreted relative to the current working directory, *not* the
+        directory of the Path object.
+
+        Returns the new Path instance pointing to the target path.
         """
         self._accessor.replace(self, target)
         return self.__class__(target)