Update the Keycloak Documentation

### Describe the bug

You deprecated this library, but you haven't updated the official Keycloak documentation here:
https://www.keycloak.org/docs/latest/securing_apps/#_nodejs_adapter

This is confusing and time-consuming and worst of all can be missed.

### Version

21

### Expected behavior

_No response_

### Actual behavior

_No response_

### How to Reproduce?

_No response_

### Anything else?

_No response_

Start with the Keycloak documentation section at https://www.keycloak.org/docs/latest/securing_apps/#_nodejs_adapter and compare its Node.js adapter guidance with the library's deprecated status. Confirm the intended replacement or wording with the issue discussion; done means the official documentation no longer presents this deprecated library as current guidance.

Written by the indexing model from the issue text.