spec.floatingIPNetwork in OpenStackFloatingIPPool no longer optional

[huxcrux]

/kind bug

What steps did you take and what happened:
When reading the API spec floatingIPNetwork is listed as optional (https://github.com/kubernetes-sigs/cluster-api-provider-openstack/blob/main/api/v1alpha1/openstackfloatingippool_types.go#L64-L66)

If I use 0.10.0-alpha.0 and not setting floatingIPNetwork i get the following error:

"error": "[OpenStackFloatingIPPool.infrastructure.cluster.x-k8s.io](http://openstackfloatingippool.infrastructure.cluster.x-k8s.io/) \"hux-lab1\" is invalid: spec.floatingIPNetwork: Invalid value: 0: spec.floatingIPNetwork in body should have at least 1 properties"}

This behaviour seems to have been changed in: #1972

What did you expect to happen:
floatingIPNetwork to be optional or for us to change it to required

Anything else you would like to add:
[Miscellaneous information that will assist in solving the issue.]

Environment:

• Cluster API Provider OpenStack version (Or git rev-parse HEAD if manually built): 0.10.0-alpha.0
• Cluster-API version: v1.6.3
• OpenStack version: Ussuri
• Minikube/KIND version: kind v0.21.0
• Kubernetes version (use kubectl version): 1.29.1
• OS (e.g. from /etc/os-release): Ubuntu 22.04