[Bug] Calling Sources in pulsar's java client prompts that Built-in source is not available

### Search before asking

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

### Version

windows 10
pulsar 3.0.0

### Minimal reproduce step

I am currently using apache/pulsar version 3.0 and need to use the sources function. I see the corresponding calling path in the api is /admin/v3/sources/ but in the java sdk org.apache.pulsar.client In the SourcesImpl of .admin.internal, I see that the built path is admin/v3/source. Is this a problem with the SDK? Or am I calling the wrong method?

### What did you expect to see?

It is expected that the interface /admin/v3/sources/{tenant}/{namespace}/{sourceName} can be used

### What did you see instead?

Built-in source is not available

### Anything else?

_No response_

### Are you willing to submit a PR?

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

Start in the Java admin client's org.apache.pulsar.client.admin.internal.SourcesImpl and compare its constructed admin/v3/source path with the expected /admin/v3/sources/{tenant}/{namespace}/{sourceName} endpoint described in the issue. Reproduce the built-in source call on Pulsar 3.0.0 on Windows 10; done means the documented sources endpoint is reached and the built-in source is no longer reported as unavailable.

Written by the indexing model from the issue text.