Use mutex when appending to error (#2201)

## Description

Make error appending thread-safe since multiple goroutines may attempt to add an error at the same time.

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

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

## Type of change

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

## Issue(s)

* closes #2197

## Test Plan

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

src/internal/connector/exchange/exchange_data_collection.go

@@ -197,7 +197,11 @@ func (col *Collection) streamItems(ctx context.Context) {
 	semaphoreCh := make(chan struct{}, urlPrefetchChannelBufferSize)
 	defer close(semaphoreCh)
 
+	updaterMu := sync.Mutex{}
 	errUpdater := func(user string, err error) {
+		updaterMu.Lock()
+		defer updaterMu.Unlock()
+
 		errs = support.WrapAndAppend(user, err, errs)
 	}