[BUG] `Microsoft.ApiManagement service/authorizationServers` support for `authorizationCodeWithPkce`

### API Spec link

https://github.com/Azure/azure-rest-api-specs/blob/main/specification/apimanagement/resource-manager/Microsoft.ApiManagement/stable/2024-05-01/definitions.json#L1743

### API Spec version

2024-05-01

### Describe the bug

To enable support for "Authorization Code + PKCE", the api spec on `grantTypes` should add support for `authorizationCodeWithPkce`. This has been supported by the Azure Portal for quite some time already.

### Expected behavior

Should be able to set grant type "Authorization Code + PKCE" on the OAuth 2.0 client for the APIM Developer Portal

### Actual behavior

grant type `authorizationCodeWithPkce` is not supported by the spec yet

### Reproduction Steps

Trying to set this grant type via Terraform, getting the following error:

### Environment

Terraform: v1.12.0
AzureRM provider: v4.28.0

Start at specification/apimanagement/resource-manager/Microsoft.ApiManagement/stable/2024-05-01/definitions.json around line 1743 and inspect the grantTypes definition. Confirm how existing grant types are represented and update the specification so authorizationCodeWithPkce is accepted. Done means the API spec supports setting Authorization Code + PKCE for an APIM OAuth 2.0 client.

Written by the indexing model from the issue text.