Update omada-v3.sh

ct/omada-v3.sh

@@ -310,7 +310,7 @@ pushd $TEMP_DIR >/dev/null
 
 export CTID=$CT_ID
 export PCT_OSTYPE=ubuntu
-export PCT_OSVERSION=20.04
+export PCT_OSVERSION=18.04
 export PCT_DISK_SIZE=$DISK_SIZE
 export PCT_OPTIONS="
   -features $FEATURES