maint: release no longer creates a diff file

Ever since commit f1cf390 (1.4.14 release), we no longer create
diff files as part of the release process.  These days, it is
assumed that it is easier to download a fresh tarball rather
than to try and use a diff file to patch an older tarball.

Signed-off-by: Eric Blake <eblake@redhat.com>
(cherry picked from commit c8a4b7c32db3a6d8d5dc7a9997df2c80ac95b030)
1 file changed