Reduce Arch Linux rootfs retention time to 2 months

https://gitlab.archlinux.org/archlinux/archlinux-docker/-/merge_requests/57

archlinux/content.md

@@ -23,7 +23,7 @@ This image is intended to serve the following goals:
 
 ## Availability
 
-Root filesystem tarballs are [provided by our GitLab](https://gitlab.archlinux.org/archlinux/archlinux-docker/-/releases) for at least a year.
+Root filesystem tarballs are [provided by our GitLab](https://gitlab.archlinux.org/archlinux/archlinux-docker/-/releases) for at least two months.
 
 ## Updating