annotateMutation will add duplicate policy names to value if mutation is re-triggered

[noahpb]

Environment

uds-core v0.26.1

Steps to reproduce

1. Apply a manifest that triggers a mutation
2. kubectl edit/patch the resource and remove the mutation
3. Watch the policy names get duplicated in the uds-core.pepr.dev/mutated annotation as the mutation gets triggered again

Expected result

No dup policy names in the uds-core.pepr.dev/mutated annotation

Actual Result

Dup policy names in the uds-core.pepr.dev/mutated annotation

Visual Proof (screenshots, videos, text, etc)

$ cat ./test-pod.yaml
apiVersion: v1
kind: Pod
metadata:
  name: init-demo
spec:
  containers:
    - name: nginx
      image: nginx
      ports:
        - containerPort: 80
      resources:
        limits:
          memory: '1Gi'
          cpu: '800m'
        requests:
          memory: '700Mi'
          cpu: '400m'
$ kubectl apply -f ./test-pod.yaml
$ kubectl get po init-demo -oyaml
apiVersion: v1
kind: Pod
metadata:
  annotations:
    uds-core.pepr.dev/mutated: '["disallow-privileged","require-non-root-user","drop-all-capabilities"]'
    uds-core.pepr.dev/uds-core-policies: succeeded
  name: init-demo
  namespace: default
...
$ kubectl edit po init-demo
***removed allowPrivilegeEscalation mutation***
$ kubectl get po init-demo -oyaml
apiVersion: v1
kind: Pod
metadata:
  annotations:
    uds-core.pepr.dev/mutated: '["disallow-privileged","require-non-root-user","drop-all-capabilities","disallow-privileged","require-non-root-user","drop-all-capabilities"]'
    uds-core.pepr.dev/uds-core-policies: succeeded
  name: init-demo
  namespace: default

Severity/Priority

low

Additional Context

Came up as I was working #698