Zookeeper fails to upgrade after upgrading operator

After upgrading the solr operator to 0.7.1 the zookeeper operator doesn't upgrade the zookeeper pods. found these errors in the logs

```
{"level":"error","ts":1694631591.8541024,"msg":"Reconciler error","controller":"zookeepercluster","controllerGroup":"zookeeper.pravega.io","controllerKind":"ZookeeperCluster","zookeeperCluster":{"name":"solr-stage-solrcloud-zookeeper","namespace":"solr-stage"},"namespace":"solr-stage","name":"solr-stage-solrcloud-zookeeper","reconcileID":"80330bbc-7a87-41db-9e5b-0d06a74c40fc","error":"Operation cannot be fulfilled on zookeeperclusters.zookeeper.pravega.io \"solr-stage-solrcloud-zookeeper\": the object has been modified; please apply your changes to the latest version and try again","stacktrace":"sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).processNextWorkItem\n\t/go/pkg/mod/sigs.k8s.io/controller-runtime@v0.12.1/pkg/internal/controller/controller.go:273\nsigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).Start.func2.2\n\t/go/pkg/mod/sigs.k8s.io/controller-runtime@v0.12.1/pkg/internal/controller/controller.go:234"}
```

zookeeper operator pod is using `0.2.15`
```
Image: pravega/zookeeper-operator:0.2.15
```
but statefulset is using an older version
```
image: pravega/zookeeper:0.2.13
```

after the operator upgrade why are those errors showing up?
why doesn't the zookeeper operator update the version in the statefulset?

Start by reproducing the operator upgrade and inspect the zookeepercluster reconciliation logs alongside the generated StatefulSet. Compare the operator image version with the StatefulSet's zookeeper image; the issue is resolved when the upgrade reconciles successfully and the StatefulSet uses the expected newer image.

Written by the indexing model from the issue text.