Unexpected behavior when changing the plugin of a `ClusterScan`

[matheusfm]

Description

It's a very specific bug that happens when we change the plugin of a ClusterScan.

How to Reproduce

1. Create a Cluster and a ClusterScan (popeye plugin by default):

   cat << EOF | kubectl apply -f -
   apiVersion: zora.undistro.io/v1alpha1
   kind: ClusterScan
   metadata:
   name: foo
   spec:
   clusterRef:
   name: foo
   schedule: "* * * * *"
   EOF

2. Wait for a successful scan (19 issues):

   NAME   CLUSTER   SCHEDULE    SUSPEND   PLUGINS   LAST STATUS   LAST SCHEDULE   LAST SUCCESSFUL   ISSUES   READY   SAAS   AGE
   foo    foo       * * * * *   false     popeye    Complete      53s             44s               19       True    OK     26m

3. Create a plugin that always fails:

   cat << EOF | kubectl apply -f -
   apiVersion: zora.undistro.io/v1alpha1
   kind: Plugin
   metadata:
   name: brutus
   namespace: zora-system
   spec:
   command:
   - /bin/sh
   - -c
   - |
     echo "ERROR" > \$(DONE_DIR)/error
     exit 27
   image: docker.io/derailed/popeye:v0.11.1
   EOF

4. Update the ClusterScan to use this plugin:

   cat << EOF | kubectl apply -f -
   apiVersion: zora.undistro.io/v1alpha1
   kind: ClusterScan
   metadata:
   name: foo
   spec:
   plugins:
   - name: brutus
   clusterRef:
   name: foo
   schedule: "* * * * *"
   EOF

5. The change does not reflect on ClusterScan that keep using popeye

   
   NAME                               CLUSTER   SCHEDULE    SUSPEND   PLUGINS   LAST STATUS   LAST SCHEDULE   LAST SUCCESSFUL   ISSUES   READY   SAAS   AGE   NEXT SCHEDULE
   clusterscan.zora.undistro.io/foo   foo       * * * * *   false     popeye    Complete      7m56s           7m47s             19       True    OK     39m   2023-03-07T13:56:00Z

NAME SCHEDULE SUSPEND ACTIVE LAST SCHEDULE AGE CONTAINERS IMAGES SELECTOR cronjob.batch/foo-popeye * False 0 56s 39m worker,popeye ghcr.io/undistro/zora/worker:v0.4.4,docker.io/derailed/popeye:v0.11.1

NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES pod/foo-popeye-27969960-t86sn 0/2 Completed 0 2m56s 10.244.0.39 kind-control-plane pod/foo-popeye-27969961-d6qx4 0/2 Completed 0 116s 10.244.0.40 kind-control-plane pod/foo-popeye-27969962-lfctl 0/2 Completed 0 56s 10.244.0.41 kind-control-plane

## Expected Behavior
The expected behavior is that the `ClusterScan` uses the new plugin.

## System Information
 - Kubernetes v1.25.3
 - Zora 0.4.4