Update cronjob-tutorial.md
s/It does the by/It does this by/
@@ -12,7 +12,7 @@ implementation of the CronJob controller in Kubernetes, and we'd like to
rewrite it using KubeBuilder.
The job (no pun intended) of the *CronJob* controller is to run one-off
-tasks on the Kubernetes cluster at regular intervals. It does the by
+tasks on the Kubernetes cluster at regular intervals. It does this by
building on top of the *Job* controller, whose task is to run one-off tasks
once, seeing them to completion.
