remove outdated postinst, cruft from old times

It was for the switch from doing our QEMU/KVM build as 'qemu' to
'kvm', see
https://git.proxmox.com/?p=pve-qemu-kvm.git;a=commitdiff;h=8b7e35182aba87372ba5da5d322791557b744c15

Based on:
https://pve.proxmox.com/pipermail/pve-devel/2019-May/037153.html

Co-developed-by: Stoiko Ivanov <s.ivanov@proxmox.com>
Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>

debian/postinst

@@ -1,66 +0,0 @@
-#!/bin/bash
-
-# Abort if any command returns an error value 
-set -e
-
-case "$1" in
-  configure)
-
-    # remove stale /etc/qemu (files are in /etc/kvm)
-    # file is now in /usr/share/kvm/cpus-x86_64.conf
-    rm -f /etc/qemu/target-x86_64.conf
-    if test -d /etc/qemu; then rmdir /etc/qemu; fi
-    rm -f /etc/kvm/target-x86_64.conf
-
-    # There are three sub-cases:
-    if test "${2+set}" != set; then
-      # We're being installed by an ancient dpkg which doesn't remember
-      # which version was most recently configured, or even whether
-      # there is a most recently configured version.
-      :
-
-    elif test -z "$2" -o "$2" = "<unknown>"; then
-      # The package has not ever been configured on this system, or was
-      # purged since it was last configured.
-      :
-
-    else
-      # Version $2 is the most recently configured version of this
-      # package.
-      :
-
-    fi ;;
-  abort-upgrade)
-    # Back out of an attempt to upgrade this package FROM THIS VERSION
-    # to version $2.  Undo the effects of "prerm upgrade $2".
-    :
-
-    ;;
-  abort-remove)
-    if test "$2" != in-favour; then
-      echo "$0: undocumented call to \`postinst $*'" 1>&2
-      exit 0
-    fi
-    # Back out of an attempt to remove this package, which was due to
-    # a conflict with package $3 (version $4).  Undo the effects of
-    # "prerm remove in-favour $3 $4".
-    :
-
-    ;;
-  abort-deconfigure)
-    if test "$2" != in-favour -o "$5" != removing; then
-      echo "$0: undocumented call to \`postinst $*'" 1>&2
-      exit 0
-    fi
-    # Back out of an attempt to deconfigure this package, which was
-    # due to package $6 (version $7) which we depend on being removed
-    # to make way for package $3 (version $4).  Undo the effects of
-    # "prerm deconfigure in-favour $3 $4 removing $6 $7".
-    :
-
-    ;;
-  *) echo "$0: didn't understand being called with \`$1'" 1>&2
-     exit 0;;
-esac
-
-exit 0