Update source URL in PKGBUILD

[UweSauter]

https://github.com/zfsonlinux/zfs.git is getting redirected to https://github.com/openzfs/zfs.git .

Update source variable in PKGBUILD to the new URL.

This is also applicable to some of the other archzfs repositories:
archzfs/zfs-utils-git
archzfs/zfs-linux-zen-git
archzfs/zfs-linux-lts-git
archzfs/zfs-linux-hardened-git
archzfs/zfs-dkms-git

The repositories that are based on releases instead of commits need to be updated from https://github.com/zfsonlinux/zfs/releases/ to https://github.com/openzfs/zfs/releases/ :
archzfs/zfs-utils
archzfs/zfs-dkms

Shall I open separate issues?