Changed enum to nonExpandable

specification/cognitiveservices/OpenAI.Inference/models/completions/azure_chat_extensions.tsp

@@ -128,11 +128,10 @@ model AzureChatExtensionRetrievedDocument {
   filterReason?: AzureChatExtensionRetrieveDocumentFilterReason;
 }
 
+#suppress "@azure-tools/typespec-azure-core/no-closed-literal-union" "Enforcing closed set of values per service release"
 /** The reason for filtering the retrieved document. */
 @added(ServiceApiVersions.v2024_05_01_Preview)
 union AzureChatExtensionRetrieveDocumentFilterReason {
-  string,
-
   /**
    * The document is filtered by original search score threshold defined by `strictness` configure.
    */

specification/cognitiveservices/data-plane/AzureOpenAI/inference/preview/2024-05-01-preview/generated.json

@@ -1220,7 +1220,7 @@
       ],
       "x-ms-enum": {
         "name": "AzureChatExtensionRetrieveDocumentFilterReason",
-        "modelAsString": true,
+        "modelAsString": false,
         "values": [
           {
             "name": "score",