docs: fix rxResource example to return object from params function (#64327)

Previously, the example returned a plain value instead of an object,
causing destructuring in the `stream` function to fail. Updated to
`params: () => ({ userId: this.userId() })` for correctness.

fixes: #64313

Update adev/src/content/ecosystem/rxjs-interop/signals-interop.md

Co-authored-by: Matthieu Riegler <kyro38@gmail.com>

PR Close #64327

adev/src/content/ecosystem/rxjs-interop/signals-interop.md

@@ -146,7 +146,7 @@ export class UserProfile {
   protected userId = input<string>();
 
   private userResource = rxResource({
-    params: () => this.userId(),
+    params: () => ({ userId: this.userId() }),
 
     // The `stream` property expects a factory function that returns
     // a data stream as an RxJS Observable.