Do not hard-code the UC20 amd64 image size anymore

debian/changelog

@@ -1,3 +1,10 @@
+livecd-rootfs (2.664.9) UNRELEASED; urgency=medium
+
+  * Do not hard-code the UC20 amd64 image size as now ubuntu-image should be
+    able to properly calculate the needed size itself.
+
+ -- Łukasz 'sil2100' Zemczak <lukasz.zemczak@ubuntu.com>  Tue, 03 Nov 2020 11:28:22 +0100
+
 livecd-rootfs (2.664.8) focal; urgency=medium
 
   Backport snap-preseed work from groovy to focal LP: #1896755

live-build/auto/config

@@ -364,9 +364,6 @@ case $IMAGEFORMAT in
 							xenial|bionic)
 								UBUNTU_IMAGE_ARGS="$UBUNTU_IMAGE_ARGS --image-size 3700M"
 								;;
-							*)
-								UBUNTU_IMAGE_ARGS="$UBUNTU_IMAGE_ARGS --image-size 8G"
-								;;
 						esac
 					fi
 					;;