api-version for .net (Azure#29121)

Author: weidongxu-microsoft

specification/devcenter/DevCenter/tspconfig.yaml

@@ -17,6 +17,7 @@ options:
     namespace: "{package-dir}"
     clear-output-folder: true
     flavor: azure
+    api-version: "2023-04-01"
   "@azure-tools/typespec-python":
     package-dir: "azure-developer-devcenter"
     package-name: "{package-dir}"