snap: release 1.6.0

bump snap version to 1.6.0

fixes #410

Signed-off-by: Julio Montes <julio.montes@intel.com>

snap/snapcraft.yaml

@@ -1,5 +1,5 @@
 name: kata-containers
-version: "1.6.0-rc1"
+version: "1.6.0"
 summary: Build lightweight VMs that seamlessly plug into the containers ecosystem
 description: |
   Kata Containers is an open source project and community working to build a