Include a note on user working hours (#1679)

Add a note that user working hours are currently hardcoded and will be
updated in a future release

# What this PR does
Adds a note that OnCall working hours are hardcoded and cannot be
customized at the moment.

## Which issue(s) this PR fixes

## Checklist

- [ ] Unit, integration, and e2e (if applicable) tests updated
- [ ] Documentation added (or `pr:no public docs` PR label added if not
required)
- [ ] `CHANGELOG.md` updated (or `pr:no changelog` PR label added if not
required)

docs/sources/calendar-schedules/web-schedule/create-schedule/index.md

@@ -22,6 +22,8 @@ your schedule, add users, reorder users, and reference teammates' time zones.
 To learn more, see [On-call schedules]({{< relref "../../../calendar-schedules" >}}) which provides the fundamental
 concepts for this task.
 
+>**Note:** User working hours are currently hardcoded and cannot be changed. Profile settings to configure this and other options will be added in a future release.
+
 ## Before you begin
 
 - Users with Admin or Editor roles can create, edit and delete schedules.