bpo-45114: Use lstat() instead of stat() in stat docs example (GH-29845)

Doc/library/stat.rst

@@ -109,7 +109,7 @@ Example::
 
        for f in os.listdir(top):
            pathname = os.path.join(top, f)
-           mode = os.stat(pathname).st_mode
+           mode = os.lstat(pathname).st_mode
            if S_ISDIR(mode):
                # It's a directory, recurse into it
                walktree(pathname, callback)