Agent Pool API cannot add nodeTaints to node pool while updating

After checked, seems taints cannot be added to node after created successfully per [document](https://docs.microsoft.com/en-us/rest/api/aks/agentpools/createorupdate#request-body). Seems when these were first introduced these could be updated, but that behavior has since changed. So could service team confirm if there's plans to change that, so this field can be updated?

Start with the linked AKS Agent Pools CreateOrUpdate request-body documentation and verify the current nodeTaints update behavior with the service team. Done means a confirmed answer about mutability and, if supported, a documented API-specification change path.

Written by the indexing model from the issue text.