documentation: replace deps.{deb,rpm}.txt with scripts

install-deps.sh installs the dependencies based on the content of
debian/control (if apt-get is found) or ceph.spec.in (if yum is
found). The manually maintained list of dependencies for deb based
operating systems (deps.deb.txt) and rpm based operating
systems (deps.rpm.txt) are deprecated.

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

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