docs: fix cross reference (#839)

Small fix for a cross reference in docs.

docs/userguide.rst

@@ -314,7 +314,7 @@ In some cases, you want to run tasks directly, without involving schedules:
 
 To queue a job and wait for its completion and get the result, the easiest way is to
 use :meth:`~Scheduler.run_job`. If you prefer to just launch a job and not wait for its
-result, use:meth:`~Scheduler.add_job` instead. If you want to get the results later, you
+result, use :meth:`~Scheduler.add_job` instead. If you want to get the results later, you
 need to pass an appropriate ``result_expiration_time`` parameter to
 :meth:`~Scheduler.add_job` so that the result is saved. Then, you can call
 :meth:`~Scheduler.get_job_result` with the job ID you got from