docs(http): fix "Expecting and answering requests" example mistake

Possibly overlooked testing documentation mistake fixed:
- `http.get('/data')` probably ought to be paired with `httpMock.expectOne('/data')` instead of `httpMock.expectOne('/data')`.

aio/content/guide/http.md

@@ -598,7 +598,7 @@ it('expects a GET request', inject([HttpClient, HttpTestingController], (http: H
     
   // At this point, the request is pending, and no response has been
   // sent. The next step is to expect that the request happened.
-  const req = httpMock.expectOne('/test');
+  const req = httpMock.expectOne('/data');
   
   // If no request with that URL was made, or if multiple requests match,
   // expectOne() would throw. However this test makes only one request to