starting with sphinx 7.2.0, root is a pathlib.Path not a string anymore

so convert it to a string, the trailing os.sep is not needed.
os.path.join which is used to join paths, expects string and inserts the
os.sep.

See-also: sphinx-doc/sphinx#11526
See-also: sphinx-doc/sphinx#11608

Signed-off-by: Martin Gysel <me@bearsh.org>
(cherry picked from commit 1293e18)

extras/sphinxtogithub/sphinxtogithub.py

@@ -98,7 +98,7 @@ class DirectoryHandler(object):
     def __init__(self, name, root, renamer):
         self.name = name
         self.new_name = name[1:]
-        self.root = root + os.sep
+        self.root = str(root)
         self.renamer = renamer
 
     def path(self):