Incorrect field label in TenantGroup view

### NetBox version

v3.0.5

### Python version

3.9

### Steps to Reproduce

Open any tenant group `/tenancy/tenant-groups/<int:pk>/`.

### Expected Behavior

A field counting all tenants in the group should be present.

### Observed Behavior

A field counting all tenants in the group is present, but incorrectly labeled `Sites`.