GH-7227 Fix application_gateway subnet documentation

[tom-dudley]

Align the documentation for the application_gateway subnet_ids with the following documentation:

• https://docs.microsoft.com/en-us/rest/api/application-gateway/applicationgateways/createorupdate#applicationgatewayipconfiguration
• https://docs.microsoft.com/en-us/rest/api/application-gateway/applicationgateways/createorupdate#frontendipconfiguration
• https://docs.microsoft.com/en-us/cli/azure/network/application-gateway/frontend-ip?view=azure-cli-latest#az-network-application-gateway-frontend-ip-create-optional-parameters
• https://docs.microsoft.com/en-us/cli/azure/network/application-gateway?view=azure-cli-latest#az-network-application-gateway-create-optional-parameters

Fixes #7227.

[ArcturusZhang]

LGTM 👍 thanks!

[tombuildsstuff]

LGTM - thanks for this @tom-dudley

[ghost]

This has been released in version 2.14.0 of the provider. Please see the Terraform documentation on provider versioning or reach out if you need any assistance upgrading. As an example:

provider "azurerm" {
    version = "~> 2.14.0"
}
# ... other configuration ...

[ghost]

I'm going to lock this issue because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.

If you feel this issue should be reopened, we encourage creating a new issue linking back to this one for added context. If you feel I made an error 🤖 🙉 , please reach out to my human friends 👉 hashibot-feedback@hashicorp.com. Thanks!