Documentation updates - Azure Front Door and WAF (#15022)

* Updated FrontDoor documentation

Clarified the year when the breaking change was made

* Added valid values for mode

website/docs/r/frontdoor.html.markdown

@@ -17,7 +17,7 @@ Below are some of the key scenarios that Azure Front Door Service addresses:
 * Use Front Door to improve application performance with SSL offload and routing requests to the fastest available application backend.
 * Use Front Door for application layer security and DDoS protection for your application.
 
-!> **Be Aware:** Azure is rolling out a breaking change on Friday 9th April which may cause issues with the CDN/FrontDoor resources. [More information is available in this Github issue](https://github.com/hashicorp/terraform-provider-azurerm/issues/11231) - however unfortunately this may necessitate a breaking change to the CDN and FrontDoor resources, more information will be posted [in the Github issue](https://github.com/hashicorp/terraform-provider-azurerm/issues/11231) as the necessary changes are identified.
+!> **Be Aware:** Microsoft rolled out a breaking change on Friday 9th April 2021 which may cause issues with the CDN/FrontDoor resources. [More information is available in this Github issue](https://github.com/hashicorp/terraform-provider-azurerm/issues/11231) - however unfortunately this may necessitate a breaking change to the CDN and FrontDoor resources, more information will be posted [in the Github issue](https://github.com/hashicorp/terraform-provider-azurerm/issues/11231) as the necessary changes are identified.
 
 !> **BREAKING CHANGE:** The `custom_https_provisioning_enabled` field and the `custom_https_configuration` block have been removed from the `azurerm_frontdoor` resource in the `v2.58.0` provider due to changes made by the service team. If you wish to enable the custom https configuration functionality within your `azurerm_frontdoor` resource moving forward you will need to define a separate `azurerm_frontdoor_custom_https_configuration` block in your configuration file.
 

website/docs/r/web_application_firewall_policy.html.markdown

@@ -166,7 +166,7 @@ The `policy_settings` block supports the following:
 
 * `enabled` - (Optional) Describes if the policy is in enabled state or disabled state. Defaults to `true`.
 
-* `mode` - (Optional) Describes if it is in detection mode or prevention mode at the policy level. Defaults to `Prevention`.
+* `mode` - (Optional) Describes if it is in detection mode or prevention mode at the policy level. Valid values are `Detection` and `Prevention`. Defaults to `Prevention`.
 
 * `file_upload_limit_in_mb` - (Optional) The File Upload Limit in MB. Accepted values are in the range `1` to `4000`. Defaults to `100`.