Add description field to TenantSerializer

This might be just an oversight.  Other data models do include the description in their serialisers.  The API produces the description field with this change.

netbox/tenancy/api/serializers.py

@@ -30,7 +30,7 @@ class TenantSerializer(CustomFieldSerializer, serializers.ModelSerializer):
 
     class Meta:
         model = Tenant
-        fields = ['id', 'name', 'slug', 'group', 'comments', 'custom_fields']
+        fields = ['id', 'name', 'slug', 'group', 'description', 'comments', 'custom_fields']
 
 
 class TenantNestedSerializer(TenantSerializer):