GRMLBASE/80-initramfs: no longer set CRYPTSETUP=y

Quoting from cryptsetup's Debian packaging git:

| commit 06f8c00c908ffd1fa95c4afc78e9cac462d01d91
| Author: Guilhem Moulin <guilhem@debian.org>
| Date:   Sat Jul 20 19:18:21 2019 -0300
|
|     initramfs: Remove compatibility warnings regarding CRYPTSETUP=[y|n].
|
|     The warning was added in 2:2.0.3-1 for the ‘cryptsetup’ package split
|     into ‘cryptsetup-run’ and ‘cryptsetup-initramfs’.  With the recent
|     Buster release we can now move on: cryptsetup is always copied to the
|     initramfs when the ‘cryptsetup-initramfs’ package is installed.

Given that we have the cryptsetup-initramfs package in GRMLBASE,
we no longer need to use this.

Closes: https://github.com/grml/grml/issues/82