MT#60283 Update to grml2usb version v0.20.6

grml2usb had 47 commits since v0.19.2 (which we used so far), time to
bump it to its most recent stable version (being v0.20.6), which is also
part of current Debian/trixie.

While at it, drop deprecated grml64-small_2018.04.11-efi workaround.

Change-Id: Iac59b6ba9cf1f3782e10dd612153cd8e451c2ea3

build_iso.sh

@@ -16,7 +16,7 @@ TEMPLATES="templates"
 GRML_URL="${GRML_URL:-https://deb.sipwise.com/deployment-iso/grml/}"
 GRML_HASH_URL="${GRML_HASH_URL:-https://deb.sipwise.com/deployment-iso/grml/}"
 SIPWISE_ISO="sip_provider_${MR}_${DATE}.iso"
-GRML2USB_VERSION='v0.19.2'
+GRML2USB_VERSION='v0.20.6'
 
 usage () {
   echo "Usage: $0 compat <grml.iso> <mr version> <Debian dist>"
@@ -45,13 +45,6 @@ else
   usage
 fi
 
-case "${GRML_ISO}" in
-  grml64-small_2018.04.11-efi*)
-    GRML2USB_VERSION='v0.14.14'
-    echo "*** NOTE: identified Grml ISO ${GRML_ISO}, falling back to grml2usb version ${GRML2USB_VERSION} for building"
-    ;;
-esac
-
 case "${GRML_ISO}" in
   grml*buster*|grml*bullseye*)
     MEMTEST_SCREENSHOT="/code/t/screenshots/01-memtest-v5.jpg"