How to delete an existing label in a deployment with helm upgrade

I have an existing deployment that has the label importance: normal in spec/template/metadata/labels (all the pods spawned from this deployment have that label in them).

The current deployment yaml does NOT have that importance: normal label in it. It was in an older version of the deployment yaml.

So everything that was deployed with the original deployment yaml has this importance label in it. After we perform a helm upgrade --install and use the latest deployment yaml(which does not have this label) and when we look at the deployment in the cluster is still has this label in it. The deployment does have the changes we made but it does not delete this old label.

I want to be able to remove that label when a helm upgrade is performed.

I tried the following trying to use the --set flag but have had no luck.

Command I tried - which did nothing:

helm upgrade --install echo service-standard/service-standard --namespace qa --set-string spec.template.metadata.labels.importance="" -f ./helm-chart/values.shared.yaml --wait --timeout 600s

I also tried using --reset-values and that also had no effect.

Here is the snippet of the deployment that I am trying to remove the label from - The label is in the first spec block (not the second) right before app: echo-selector :

apiVersion: apps/v1kind: Deploymentmetadata:  annotations:    deployment.kubernetes.io/revision: "8"  creationTimestamp: "2022-12-14T15:24:04Z"  generation: 9  labels:    app.kubernetes.io/managed-by: Helm  name: echo-deploymentspec:  replicas: 2  revisionHistoryLimit: 5  template:    metadata:      annotations:        linkerd.io/inject: enabled      creationTimestamp: null      labels:        app: echo-selector        importance: normal        version: current    spec:      containers:      - env:        - name: TEST

We do not want to have to delete the deployment and re install it (which would remove the label).Any help or advice is greatly appreciated!!!!