Drop e2fsprogs scratch build workaround
Drop the e2fsprogs scratch build workaround we were using for
https://github.com/fedora-silverblue/issue-tracker/issues/470 -
with the new 'use a custom ref and rebase to the official ref'
thing I implemented for update ostree tests, it shouldn't be
necessary any longer.
Signed-off-by: Adam Williamson <awilliam@redhat.com>