message: docs(navigation): remove duplicated nav link
  Remove the duplicated 'Operator' side nav link.
diff: "url": "guide/subject",
  "title": "Subjects"
  },
  - {
  - "url": "guide/operators",
  - "title": "Operators"
  - },
  {
  "url": "guide/scheduler",
  "title": "Scheduler"
  