fix(docs-infra): fix the retry-on-error example (#38905)

Previously, the `retry` example did not work as intended. The `retry`
operator was called before the exception occured, thus not retrying the
`ajax` request.

This commit moves the `retry` operator into the correct order to ensure
that the failed request is retried.

PR Close #38905

aio/content/examples/rx-library/src/retry-on-error.ts

@@ -8,13 +8,13 @@ import { ajax } from 'rxjs/ajax';
 import { map, retry, catchError } from 'rxjs/operators';
 
 const apiData = ajax('/api/data').pipe(
-  retry(3), // Retry up to 3 times before failing
   map(res => {
     if (!res.response) {
       throw new Error('Value expected!');
     }
     return res.response;
   }),
+  retry(3), // Retry up to 3 times before failing
   catchError(err => of([]))
 );