message: docs(aio): Fix http guide
diff: @@ -335,7 +335,7 @@ If you have a need to mutate the request body, you need to copy the request body
  Since requests are immutable, they cannot be modified directly. To mutate them, use `clone()`:
  ```javascript
  -intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpError<any>> {
  +intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
  // This is a duplicate. It is exactly the same as the original.
  const dupReq = req.clone();
  