Remove event instance backup issue from known issues (#3775)

Missed removing this from the known issues list when the issue was fixed.

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#### Does this PR need a docs update or release note?

- [ ] ✅ Yes, it's included
- [ ] 🕐 Yes, but in a later PR
- [ ] ⛔ No

#### Type of change

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- [ ] 🌻 Feature
- [ ] 🐛 Bugfix
- [ ] 🗺️ Documentation
- [ ] 🤖 Supportability/Tests
- [ ] 💻 CI/Deployment
- [ ] 🧹 Tech Debt/Cleanup

#### Issue(s)

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#### Test Plan

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- [ ] 💪 Manual
- [ ] ⚡ Unit test
- [ ] 💚 E2E

website/docs/support/known-issues.md

@@ -20,9 +20,6 @@ Below is a list of known Corso issues and limitations:
   while a backup is being created will be included in the running backup.
   Future backups run when the data isn't modified will include the data.
 
-* Exchange Calender Event instance exceptions (changes to a single event within a recurring series) aren't
-included in backup and restore.
-
 * SharePoint document library data can't be restored after the library has been deleted.
 
 * Sharing information of items in OneDrive/SharePoint using sharing links aren't backed up and restored.