DeletePodForUpdate reports NotFound as a rolling-update delete error

Hi Solr Operator maintainers,

While looking at the managed rolling update path, I noticed that `DeletePodForUpdate` appears to treat an already-deleted pod as an error.

`handleManagedCloudRollingUpdate` calls `DeletePodForUpdate` for pods selected for update:

[`controllers/solr_cluster_ops_util.go:508-L510`](https://github.com/apache/solr-operator/blob/32bb7987a02a3491483563564b99a03ebb4bda77/controllers/solr_cluster_ops_util.go#L508-L510)

Inside `DeletePodForUpdate`, once the pod is ready to be deleted, the helper deletes it with a UID precondition:

[`controllers/solr_pod_lifecycle_util.go:102-L107`](https://github.com/apache/solr-operator/blob/32bb7987a02a3491483563564b99a03ebb4bda77/controllers/solr_pod_lifecycle_util.go#L102-L107)

That UID precondition is useful because it avoids deleting a replacement pod with the same name. But if the target pod is already gone, the helper currently logs the delete error and records a `PodUpdateError` event:

[`controllers/solr_pod_lifecycle_util.go:108-L111`](https://github.com/apache/solr-operator/blob/32bb7987a02a3491483563564b99a03ebb4bda77/controllers/solr_pod_lifecycle_util.go#L108-L111)

I do not see an `apierrors.IsNotFound` case around that delete. A possible sequence is:

```text
managed rolling update selects pod P for update
DeletePodForUpdate prepares P for deletion
P is already deleted by a previous reconcile attempt or another controller action
the cached rolling-update state still includes P
r.Delete(ctx, P, UID precondition) returns NotFound
DeletePodForUpdate reports PodUpdateError even though P is already absent
```

For this update path, absence of the old pod seems to be the desired postcondition: the StatefulSet can recreate it with the updated spec. Would it be reasonable to treat `apierrors.IsNotFound(err)` from this delete as success, while still keeping the UID precondition for the non-NotFound case?

For example, the delete branch could avoid logging/returning a warning for NotFound and only report other delete errors.

Start with handleManagedCloudRollingUpdate in controllers/solr_cluster_ops_util.go and DeletePodForUpdate in controllers/solr_pod_lifecycle_util.go, focusing on the delete branch at the referenced lines. Check how the existing rolling-update flow reports PodUpdateError events. Done means an already-absent pod is treated as successful while other delete errors still produce the existing warning and event.

Written by the indexing model from the issue text.