documentation: replace deps.deb.txt with a script

display-deps.sh creates the list of dependencies based on the content
of debian/control. The manually maintained list of dependencies for
debian based operating systems (deps.deb.txt) is deprecated.

http://tracker.ceph.com/issues/10175 Fixes: #10175

Signed-off-by: Loic Dachary <ldachary@redhat.com>