[Doc] Ack cumulative is not possible in key_shared subscriptions

### Search before asking

- [X] I searched in the [issues](https://github.com/apache/pulsar/issues) and found nothing similar.

### What issue do you find in Pulsar docs?

we shouldn't ack cumulatively on the shared or key-shared subscription.

### What is your suggestion?

Add it

### Any reference?

_No response_

### Are you willing to submit a PR?

- [X] I'm willing to submit a PR!

Locate the Pulsar documentation covering shared and key_shared subscriptions and review how acknowledgment behavior is described. Add clear guidance that cumulative acknowledgment should not be used with these subscription types, then verify the documentation consistently reflects that limitation.

Written by the indexing model from the issue text.