Fix test related to default image version

[dobrerazvan]

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• Failure [0.001 seconds]
ZookeeperCluster Types
/Users/dobre/work/zookeeper-operator/api/v1beta1/zookeepercluster_types_test.go:26
  #WithDefaults
  /Users/dobre/work/zookeeper-operator/api/v1beta1/zookeepercluster_types_test.go:36
    Image
    /Users/dobre/work/zookeeper-operator/api/v1beta1/zookeepercluster_types_test.go:62
      Checking tostring() function [It]
      /Users/dobre/work/zookeeper-operator/api/v1beta1/zookeepercluster_types_test.go:81

      Expected
          <string>: ghcr.io/adobe/zookeeper-operator/zookeeper:3.8.4-0.2.15-adobe-20250923
      to equal
          <string>: pravega/zookeeper:0.2.15

      /Users/dobre/work/zookeeper-operator/api/v1beta1/zookeepercluster_types_test.go:82
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Summarizing 1 Failure:

[Fail] ZookeeperCluster Types #WithDefaults Image [It] Checking tostring() function 
/Users/dobre/work/zookeeper-operator/api/v1beta1/zookeepercluster_types_test.go:82