Correct typo in CI_PIPELINE_SOURCE string comparison

doc/ci/jobs/job_control.md

@@ -777,7 +777,7 @@ job1:
     - echo
   rules:
     - if: $CI_PIPELINE_SOURCE == "merge_request_event"
-    - if: $CI_PIPELINE_SOURCE == "scheduled"
+    - if: $CI_PIPELINE_SOURCE == "schedule"
     - if: $CI_PIPELINE_SOURCE == "push"
       when: never
 ```