Events get duplicated in the sidebar when an external program modifies them

### What Happened?

I have an Outlook iCalendar file that I wanted to be able to view from elementary Calendar. Since syncing from a remote `.ics` file is not supported (only option is a one-time import of a local `.ics` file), I configured syncing from Evolution directly with a refresh of 15 minutes.

After a few hours I noticed when opening Calendar that events were duplicated several times in the sidebar (but not the calendar view).

Killing Calendar and restarting it clears the duplicated event, but refreshing makes them appear again.

### Steps to Reproduce

1. Configure a remote iCalendar in Evolution
2. Open elementary Calendar
3. Right-click the remote calendar in Evolution and click "Refresh", repeat this a few times
4. See events get duplicated in elementary Calendar

### Expected Behavior

Events do not get duplicated.

### OS Version

8.x (Circe)

### OS Architecture

amd64 (on most hardwares)

### Session Type

Secure Session (Wayland, This is the default)

### Software Version

Latest release (I have run all updates)

### Log Output

```shell

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### Hardware Info

_No response_