version: add new docker version entry for agent test on arm

make proto in agent test on arm64 will fail when using docker 18.06
and using docker 19.03 can avoid that failure. So a new entry of
docker version for agent on arm64 is added.

Signed-off-by: Jianyong wu <jianyong.wu@arm.com>
Fixes: kata-containers#3056

versions.yaml

@@ -215,6 +215,10 @@ externals:
     version: "v18.06-ce"
     meta:
       swarm-version: "1.12.1"
+    architecture:
+      aarch64:
+        agent:
+          version: "v19.03-ce"
 
   kubernetes:
     description: "Kubernetes project container manager"