Merge pull request #1227 from k8s-infra-cherrypick-robot/cherry-pick-1226-to-release-0.6

[release-0.6] 🌱 Add release 0.6.x to metadata.yaml

Author: k8s-ci-robot

metadata.yaml

@@ -10,3 +10,6 @@ releaseSeries:
 - major: 0
   minor: 5
   contract: v1beta1
+- major: 0
+  minor: 6
+  contract: v1beta1