fix: allow chart to be upgradable

[lae]

Removes chart name/version from selector labels, which for StatefulSets are meant to be immutable. This seems to be what other chart maintainers have done, e.g. elastic/helm-charts#622

see helm/charts#7680

This fixes the following error when upgrading a helm release to a newer chart version:

- app_version: v25.0.0-preview6
  chart: dgraph-25.0.0-preview6
  description: 'Upgrade "dgraph" failed: cannot patch "dgraph-dgraph-ratel" with kind
    Deployment: Deployment.apps "dgraph-dgraph-ratel" is invalid: spec.selector: Invalid
    value: v1.LabelSelector{MatchLabels:map[string]string{"app":"dgraph", "chart":"dgraph-25.0.0-preview6",
    "component":"ratel", "release":"dgraph"}, MatchExpressions:[]v1.LabelSelectorRequirement(nil)}:
    field is immutable && cannot patch "dgraph-dgraph-alpha" with kind StatefulSet:
    StatefulSet.apps "dgraph-dgraph-alpha" is invalid: spec: Forbidden: updates to
    statefulset spec for fields other than ''replicas'', ''ordinals'', ''template'',
    ''updateStrategy'', ''persistentVolumeClaimRetentionPolicy'' and ''minReadySeconds''
    are forbidden && cannot patch "dgraph-dgraph-zero" with kind StatefulSet: StatefulSet.apps
    "dgraph-dgraph-zero" is invalid: spec: Forbidden: updates to statefulset spec
    for fields other than ''replicas'', ''ordinals'', ''template'', ''updateStrategy'',
    ''persistentVolumeClaimRetentionPolicy'' and ''minReadySeconds'' are forbidden'
  revision: 6
  status: failed
  updated: "2025-09-18T22:17:57.424354119Z"

Still requires deleting StatefulSets (or running helm with --force?) for existing deployments though to remove the problematic label, I think.