release v1.3: mention openSUSE
release v1.3: mention openSUSE

Buildah v1.3 is already in openSUSE Tumbleweed, so let's put it on the
list of Buildah-shipping distributions.

Signed-off-by: Valentin Rothberg <vrothberg@suse.com>

Closes: #915
Approved by: rhatdan

TomSweeneyRedHat/buildah,ipbabble/buildah,nalind/buildah-1,projectatomic/buildah,nalind/buildah,ipbabble/buildah,nalind/buildah-1,rhatdan/buildah,projectatomic/buildah,rhatdan/buildah,projectatomic/buildah,TomSweeneyRedHat/buildah,nalind/buildah-1,TomSweeneyRedHat/buildah,rhatdan/buildah,nalind/buildah