[clarification][Doc] bouncy castle providers only support JCE not JSSE

### 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?

Pulsar only supports BC implementation of JCE for end-to-end encryption.
We do not implement JSSE (date encryption in transit).
But the doc structure gives users an impression that pulsar support data in transit encryption using bouncy castle.

### What is your suggestion?

Please add clarification in the doc or restructure to avoid the confusion.

### Any reference?

_No response_

### Are you willing to submit a PR?

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