MT#56773 deployment.sh: assume bookworm by default and drop deprecated workarounds

We no longer install any system with bullseye by default (we're using
bookworm internally and starting with trixie support f.e. for NGCP).

The buster workaround LVM support on Debian/buster and the dpkg
workaround for stretch/buster are no longer relevant.

Change-Id: Id96c0c1ce2b49d6332a4eb092a9f559dc221e607

templates/scripts/includes/deployment.sh

@@ -1517,7 +1517,7 @@ ARCH=$(dpkg --print-architecture)
 CARRIER_EDITION=false
 CE_EDITION=false
 CROLE=''
-DEBIAN_RELEASE='bullseye'
+DEBIAN_RELEASE='bookworm'
 DEBIAN_REPO_HOST="debian.sipwise.com"
 DEBIAN_REPO_TRANSPORT="https"
 DEBUG_MODE=false
@@ -1877,25 +1877,6 @@ if [ -e /dev/virtio-ports/org.qemu.guest_agent.0 ] ; then
   systemctl start qemu-guest-agent
 fi
 
-# this is important for "buster", do not update the string for "bullseye" or
-# future releases
-case "${DEBIAN_RELEASE}" in
-  buster)
-    UPGRADE_PACKAGES=()
-    echo "Upgrading grml-scripts + grml-debootstrap for usage with LVM on Debian/buster"
-
-    if ! check_package_version grml-scripts 2.8.4 ; then
-      UPGRADE_PACKAGES+=( grml-scripts )
-    fi
-
-    if ! check_package_version grml-debootstrap 0.86 ; then
-      UPGRADE_PACKAGES+=( grml-debootstrap )
-    fi
-
-    ensure_recent_package_versions
-    ;;
-esac
-
 if ! "$NGCP_INSTALLER" ; then
   CARRIER_EDITION=false
   PRO_EDITION=false
@@ -2260,19 +2241,6 @@ if [ -d "${TARGET}/var/lib/apt/lists/auxfiles" ]; then
   rmdir "${TARGET}/var/lib/apt/lists/auxfiles"
 fi
 
-# MT#57643: dpkg >=1.20.0 (as present on Debian/bookworm and newer) no
-# longer creates /var/lib/dpkg/available (see #647911). mmdebstrap relies
-# on and uses dpkg of the host system. But on Debian releases until and
-# including buster, dpkg fails to operate with e.g. `dpkg
-# --set-selections`, if /var/lib/dpkg/available doesn't exist, so let's
-# ensure /var/lib/dpkg/available exists on Debian releases <=buster.
-case "${DEBIAN_RELEASE}" in
-  stretch|buster)
-    echo "Generating /var/lib/dpkg/available to work around dpkg >=1.20.0 issue for Debian release '${DEBIAN_RELEASE}'"
-    chroot "${TARGET}" /usr/lib/dpkg/methods/apt/update /var/lib/dpkg
-    ;;
-esac
-
 # MT#7805
 if "$NGCP_INSTALLER" ; then
   cat << EOT | augtool --root="$TARGET"