lang/python-doc-html: Fix distinfo of v2.7.18

No content changed, it seems just Sphinx output was changed.

PR: 255782
Submitted by: Yasuhiro KIMURA <yasu@utahime.org>
Approved by: python (with hat)

(cherry picked from commit 37f19e9f90c85122bb88346c1ecc8a4540bd136c)