Merge pull request #2647 from k8s-infra-cherrypick-robot/cherry-pick-2642-to-release-1.5

[release-1.5] update metadata.yaml in preparation for v1.5.0 release

Author: k8s-ci-robot

metadata.yaml

@@ -29,3 +29,6 @@ releaseSeries:
   - major: 1
     minor: 4
     contract: v1beta1
+  - major: 1
+    minor: 5
+    contract: v1beta1