server.extraLabels missing on statefulset

**Describe the bug**
Setting server.extraLabels only applies labels to pods and not to the statefulset itself.

**To Reproduce**
Steps to reproduce the behavior:
1. Install chart with server.extraLabels set
2. Look at statefulset

**Expected behavior**
Labels should be applied to the statefulset

**Environment**
* Kubernetes version: EKS 1.24
* Distribution or cloud vendor (OpenShift, EKS, GKE, AKS, etc.):
* Other configuration options or runtime services (istio, etc.):
* vault-helm version: 0.24.1

Chart values:

```yaml
# Paste your user-supplied values here (`helm get values `).
# Be sure to scrub any sensitive values!
server:
extraLabels:
tags.datadoghq.com/service: vault
```

**Additional context**
We're setting up Datadog and the statefulset should be labelled aswell.

Start by installing the chart with the shown server.extraLabels values and inspect the generated StatefulSet alongside the pod labels. Trace how server.extraLabels is applied in the chart templates, then verify that the requested labels appear on the StatefulSet as well as the pods.

Written by the indexing model from the issue text.