[MM-15300] Migrate "Preference.PermanentDeleteByUser" to Sync by default (#10860)

* [MM-15300] Migrate "Preference.PermanentDeleteByUser" to Sync by default

* [MM-15300] Fixed readability on the SQL statement

app/user.go

@@ -1435,8 +1435,8 @@ func (a *App) PermanentDeleteUser(user *model.User) *model.AppError {
 		return err
 	}
 
-	if result := <-a.Srv.Store.Preference().PermanentDeleteByUser(user.Id); result.Err != nil {
-		return result.Err
+	if err := a.Srv.Store.Preference().PermanentDeleteByUser(user.Id); err != nil {
+		return err
 	}
 
 	if result := <-a.Srv.Store.Channel().PermanentDeleteMembersByUser(user.Id); result.Err != nil {