Revert "cryptsetup: umount encrypted devices before detaching it during shutdown"

This reverts commit 362c3782.

This commit introduced an ordering loop: remote-cryptsetup.target was both
before and after remote-fs-pre.target. It also globally ordered all cryptsetup
volumes before all mounts. Such global ordering is problematic if people have
stacked storage. Let's look for a different solution.

See https://github.com/systemd/systemd/pull/14378#discussion_r359460109.