agnhost: promote 2.54

Includes enhancements to the pause command: it now writes a termination
message (kubernetes/kubernetes#131588) and avoids a
race condition (kubernetes/kubernetes#131028).

    $ docker pull gcr.io/k8s-staging-e2e-test-images/agnhost:2.54
    2.54: Pulling from k8s-staging-e2e-test-images/agnhost
    ...
    Digest: sha256:e729df863cf62ba0363b611302784bc4b2fa79effcd057e7342bd22658ccb71d

Author: pohly

registry.k8s.io/images/k8s-staging-e2e-test-images/images.yaml

@@ -30,6 +30,7 @@
     "sha256:488b351e3b19126c378adadd4a2405519dd3ee2533bf172e7c7be0642660ce78": ["2.51"]
     "sha256:b173c7d0ffe3d805d49f4dfe48375169b7b8d2e1feb81783efd61eb9d08042e6": ["2.52"]
     "sha256:99c6b4bb4a1e1df3f0b3752168c89358794d02258ebebc26bf21c29399011a85": ["2.53"]
+    "sha256:e729df863cf62ba0363b611302784bc4b2fa79effcd057e7342bd22658ccb71d": ["2.54"]
 - name: apparmor-loader
   dmap:
     "sha256:60629fe42de6260c9b930b48a2923b69168dc1c71fa5f762f70036477ffd74b6": ["1.2"]