Fix the overlay.xml for github
Fix the overlay.xml for github

Trying to fix the layman -S warning :
 * Overlay "guillaumeseren" could not be found in the remote lists.
 * Please check if it has been renamed and re-add if necessary.

https://api.gentoo.org/overlays/repositories.xml

GuillaumeSeren/gentoo-overlay,GuillaumeSeren/gentoo-overlay