googlephotos: fix "concurrent map write" error - fixes #4003

This adds a bit of missed locking around the uploaded info to fix the
concurrent map write.

All the other accesses have locking - this one must have got missed.

backend/googlephotos/googlephotos.go

@@ -1003,7 +1003,9 @@ func (o *Object) Update(ctx context.Context, in io.Reader, src fs.ObjectInfo, op
 
 	// Add upload to internal storage
 	if pattern.isUpload {
+		o.fs.uploadedMu.Lock()
 		o.fs.uploaded.AddEntry(o)
+		o.fs.uploadedMu.Unlock()
 	}
 	return nil
 }