systemd: drop 0017-Fix-mount-option-x-initrd.mount-handling-35268-16.patch

This was simply undoing a hunk from
0008-Don-t-try-to-unmount-nix-or-nix-store.patch, so drop that one from
there and omit
0017-Fix-mount-option-x-initrd.mount-handling-35268-16.patch entirely.