bump the root filesystem size
a. pre-empt future compose failure due to running out of space
b. existing l-i-t-d persistent root feature depends on the free space on this file system, right now free space is just under 650M and is a bit tight
c. fairly certain free space dropping below 90% is why I'm running into https://bugzilla.redhat.com/show_bug.cgi?id=1715699