Original code was switching based on the ItemType, but SharePoint historically used the OneDriveItem ItemType, making the system think it should be updating a OneDriveItemInfo struct instead of a SharePointItemInfo struct.
Also add a regression test for older backup formats.
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#### Does this PR need a docs update or release note?
- [x] ✅ Yes, it's included
- [ ] 🕐 Yes, but in a later PR
- [ ] ⛔ No
#### Type of change
- [ ] 🌻 Feature
- [x] 🐛 Bugfix
- [ ] 🗺️ Documentation
- [ ] 🤖 Supportability/Tests
- [ ] 💻 CI/Deployment
- [ ] 🧹 Tech Debt/Cleanup
#### Issue(s)
* closes#3306
#### Test Plan
- [ ] 💪 Manual
- [x] ⚡ Unit test
- [ ] 💚 E2E
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