Caveats when using application registration plugin

### Where is the problem?

https://docs.konghq.com/hub/kong-inc/application-registration/

### What happened?

We need to add this as a note for the plugin.

The application registration plugin will not work correctly for a service where the ACL plugin is already enabled. Either the application registration plugin should be enabled or the ACL plugin should be enabled.

### What did you expect to happen?

If you enable application registration plugin on a service where ACL is already enabled then the developer applications will not be able to access the resources even though they have been granted access. This is because ACL will block them.

### Code of Conduct and Community Expectations

- [X] I agree to follow this project's Code of Conduct
- [X] I agree to abide by the Community Expectations

Open the application registration plugin page at https://docs.konghq.com/hub/kong-inc/application-registration/ and locate its notes or caveats section. Document that the application registration and ACL plugins should not both be enabled on the same service because ACL can block developer applications, then verify the rendered documentation page.

Written by the indexing model from the issue text.