change aws-mock image to use 8.8.59

zenko/cloudserver:latest points to an older version of cloudserver.
Update aws-mock to use ghcr.io/scality/cloudserver:8.8.59 enables us to
use the right version of cloudserver.
This has been discovered while trying to bump cloudserver
to 9.3.0-preview.1 with aws sdk v3.
Issue: ZENKO-5134

Author: benzekrimaha

.github/scripts/mocks/aws-mock.yaml

@@ -57,7 +57,7 @@ metadata:
     component: mock
 spec:
   initContainers:
-  - image: zenko/cloudserver:latest
+  - image: ghcr.io/scality/cloudserver:8.8.59
     name: setup
     imagePullPolicy: Always
     command: ["tar", "-xvf", "/static-config/mock-metadata.tar.gz", "-C", "/usr/src/app"]
@@ -67,7 +67,7 @@ spec:
     - name: metadata
       mountPath: /usr/src/app/localMetadata
   containers:
-  - image: zenko/cloudserver:latest
+  - image: ghcr.io/scality/cloudserver:8.8.59
     name: aws-mock
     ports:
       - containerPort: 80