python3-git: upgrade 3.1.24 -> 3.1.26

Changelog:
=========
Fixes a leaked file descriptor when reading the index, which would cause make
writing a previously read index on windows impossible.
See https://github.com/gitpython-developers/GitPython/issues/1395

 for details.

Signed-off-by: Wang Mingyu <wangmy@fujitsu.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>