fix a misspelling

Author: ms-henglu

website/docs/r/kubernetes_cluster.html.markdown

@@ -456,7 +456,7 @@ An `ingress_application_gateway` block supports the following:
 
 * `subnet_id` - (Optional) The ID of the subnet on which to create an Application Gateway, which in turn will be integrated with the ingress controller of this Kubernetes Cluster. See [this](https://docs.microsoft.com/en-us/azure/application-gateway/tutorial-ingress-controller-add-on-new) page for further details.
 
--> **NOTE** If using `enabled` in conjunction with `only_critical_addons_enabled`, the AGIC pod will fail to start. A seperate `azurerm_kubernetes_cluster_node_pool` is required to run the AGIC pod successfully. This is because AGIC is classed as a "non-critical addon". 
+-> **NOTE** If using `enabled` in conjunction with `only_critical_addons_enabled`, the AGIC pod will fail to start. A separate `azurerm_kubernetes_cluster_node_pool` is required to run the AGIC pod successfully. This is because AGIC is classed as a "non-critical addon". 
 
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