travis: Merge matrix entries.

It's not possible to use 'matrix' twice.  This makes travis to use
the latest one dropping all the osx and arm64 jobs.

Fixes: 00d3374 ("travis: Test build of debian packages.")
Acked-by: Aaron Conole <aconole@redhat.com>
Signed-off-by: Ilya Maximets <i.maximets@ovn.org>

.travis.yml

@@ -66,9 +66,6 @@ matrix:
     - arch: arm64
       compiler: clang
       env: OPTS="--disable-ssl"
-
-matrix:
-  include:
     - env: DEB_PACKAGE=1
       addons:
         apt: