Fix the link on the "edit page" button

[Drsheppard01]

When you click on the button to change the page, an error occurs. the content folder has been split into 2: ja and en (translations)

Correct link for default (English version): https://github.com/mate-desktop/mate-wiki/edit/master/content/en/_index.md

[mbkma]

This is now fixed upstream, so we need to update the geekdoc theme version.