Bug 18907: Build has deprecating message

Bug 18907: Build has deprecating message

Following the instructions at:
https://wiki.koha-community.org/wiki/Building_Debian_Packages_-_The_Easy_Way
Receiving the following message in the build:
dpkg-source: warning: relation < is deprecated: use << or <=

This patch tweaks the list-deps.
git diff origin/master -- debian/list-deps shows just the one line
changed from < to << as per the messages suggestion and eythian's
suggestion on IRC:
http://irc.koha-community.org/koha/2017-07-06#i_1950698

The control file can be regenerated from the command-line:
./debian/update-control
However, it will be attached separately.

Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>