Merge pull request #7957 from joshjms/publish-image-3.5.21

Add etcd 3.5.21

Author: k8s-ci-robot

registry.k8s.io/images/k8s-staging-etcd/images.yaml

@@ -18,6 +18,7 @@
     "sha256:a6dc63e6e8cfa0307d7851762fa6b629afb18f28d8aa3fab5a6e91b4af60026a": ["3.5.15-0"]
     "sha256:c6a9d11cc5c04b114ccdef39a9265eeef818e3d02f5359be035ae784097fdec5": ["3.5.16-0"]
     "sha256:b4a9e4a7e1cf08844c7c4db6a19cab380fbf0aad702b8c01e578e9543671b9f9": ["3.5.17-0"]
+    "sha256:d58c035df557080a27387d687092e3fc2b64c6d0e3162dc51453a115f847d121": ["3.5.21-0"]
     "sha256:13f53ed1d91e2e11aac476ee9a0269fdda6cc4874eba903efd40daf50c55eee5": ["3.5.3-0"]
     "sha256:6f72b851544986cb0921b53ea655ec04c36131248f16d4ad110cb3ca0c369dc1": ["3.5.4-0"]
     "sha256:b83c1d70989e1fe87583607bf5aee1ee34e52773d4755b95f5cf5a451962f3a4": ["3.5.5-0"]