Move chinese translation to correct locale code

This was preventing the translation from being displayed.
See wger-project/react#1123

Author: rolandgeider

wger/locale/zh_CN/LC_MESSAGES/django.po renamed to wger/locale/zh_Hans/LC_MESSAGES/django.po

@@ -19,7 +19,7 @@ msgstr ""
 "Last-Translator: KW Lam <[email protected]>\n"
 "Language-Team: Chinese (Simplified Han script) <https://hosted.weblate.org/"
 "projects/wger/web/zh_Hans/>\n"
-"Language: zh_CN\n"
+"Language: zh_Hans\n"
 "MIME-Version: 1.0\n"
 "Content-Type: text/plain; charset=UTF-8\n"
 "Content-Transfer-Encoding: 8bit\n"