"empty" commit: update changelog.po date

... just to trigger an updated (supposed to fix an issue) post-recv
git hook.

zh_CN/chapter01/changelog.po

@@ -2,7 +2,7 @@
 msgid ""
 msgstr ""
 "Project-Id-Version: PACKAGE VERSION\n"
-"POT-Creation-Date: 2020-07-01 04:04+0800\n"
+"POT-Creation-Date: 2020-07-01 04:25+0800\n"
 "PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n"
 "Last-Translator: FULL NAME <EMAIL@ADDRESS>\n"
 "Language-Team: LANGUAGE <LL@li.org>\n"