Add note about skipping attachment fetch errors (#3626)

https://github.com/alcionai/corso/pull/3607#discussion_r1229799665

---

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

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

#### Type of change

<!--- Please check the type of change your PR introduces: --->
- [ ] 🌻 Feature
- [ ] 🐛 Bugfix
- [ ] 🗺️ Documentation
- [ ] 🤖 Supportability/Tests
- [ ] 💻 CI/Deployment
- [ ] 🧹 Tech Debt/Cleanup

#### Issue(s)

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* #<issue>

#### Test Plan

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

src/pkg/services/m365/api/mail.go

@@ -406,6 +406,9 @@ func (c Mail) GetItem(
 			ByAttachmentId(ptr.Val(a.GetId())).
 			Get(ctx, attachConfig)
 		if err != nil {
+			// CannotOpenFileAttachment errors are not transient and
+			// happens possibly from the original item somehow getting
+			// deleted from M365 and so we can skip these
 			if graph.IsErrCannotOpenFileAttachment(err) {
 				logger.CtxErr(ctx, err).
 					With(