Make sure the final schedule is refreshed after dropping the cached ical
representations (sometimes the refresh final task was completed before
the cached ical files were refreshed).
This should fix task error as seen in logs, trying to parse an empty
string as ical value:
```
Task apps.schedules.tasks.refresh_ical_files.refresh_ical_file[] raised unexpected: ValueError("Found no components where exactly one is required: ''")
```
* New ical comparision func
* Add support for field `sequence` for custom on-call shifts
* Fix ical comparison
* New ical comparision func 2
* fix
* Revert "Add support for field `sequence` for custom on-call shifts"
This reverts commit b7b18d5a
Co-authored-by: Julia <ferril.darkdiver@gmail.com>