docs: fix non-working example in the `Observables` section (#34705)

PR Close #34705

aio/content/examples/observables/src/geolocation.ts

@@ -5,28 +5,39 @@ import { Observable } from 'rxjs';
 // Create an Observable that will start listening to geolocation updates
 // when a consumer subscribes.
 const locations = new Observable((observer) => {
-  // Get the next and error callbacks. These will be passed in when
-  // the consumer subscribes.
-  const {next, error} = observer;
-  let watchId;
+  let watchId: number;
 
   // Simple geolocation API check provides values to publish
   if ('geolocation' in navigator) {
-    watchId = navigator.geolocation.watchPosition(next, error);
+    watchId = navigator.geolocation.watchPosition((position: Position) => {
+      observer.next(position);
+    }, (error: PositionError) => {
+      observer.error(error);
+    });
   } else {
-    error('Geolocation not available');
+    observer.error('Geolocation not available');
   }
 
   // When the consumer unsubscribes, clean up data ready for next subscription.
-  return {unsubscribe() { navigator.geolocation.clearWatch(watchId); }};
+  return {
+    unsubscribe() {
+      navigator.geolocation.clearWatch(watchId);
+    }
+  };
 });
 
 // Call subscribe() to start listening for updates.
 const locationsSubscription = locations.subscribe({
-  next(position) { console.log('Current Position: ', position); },
-  error(msg) { console.log('Error Getting Location: ', msg); }
+  next(position) {
+    console.log('Current Position: ', position);
+  },
+  error(msg) {
+    console.log('Error Getting Location: ', msg);
+  }
 });
 
 // Stop listening for location after 10 seconds
-setTimeout(() => { locationsSubscription.unsubscribe(); }, 10000);
+setTimeout(() => {
+  locationsSubscription.unsubscribe();
+}, 10000);
 // #enddocregion