fix(doc): problematic polling operation for lro delete

Currently in the offical guide, the same polling operation is shared by all lro operations, which could cause problems for some emitters since the lro metadata contains value which doesn't fit for lro delete. See Azure/autorest.csharp#4827
This commit will create a separate polling operation which fits lro delete. The same definition is already available in https://github.com/Azure/typespec-azure/blob/955fc9534c2f7153d45c9fbe5743baa0c104d803/packages/samples/specs/data-plane/trait-versioning/main.tsp#L72-L77

docs/getstarted/azure-core/step06.md

@@ -17,9 +17,14 @@ alias ServiceTraits = SupportsRepeatableRequests &
 alias Operations = Azure.Core.ResourceOperations<ServiceTraits>;
 
 interface Widgets {
+  @sharedRoute
   @doc("Gets status of a Widget operation.")
   getWidgetOperationStatus is Operations.GetResourceOperationStatus<Widget>;
 
+  @sharedRoute
+  @doc("Gets status of a Widget delete operation.")
+  getWidgetDeleteOperationStatus is Operations.GetResourceOperationStatus<Widget, never>;
+
   @doc("Fetch a Widget by name.")
   getWidget is Operations.ResourceRead<Widget>;
 
@@ -28,7 +33,7 @@ interface Widgets {
   createOrUpdateWidget is Operations.LongRunningResourceCreateOrUpdate<Widget>;
 
   @doc("Delete a Widget asynchronously.")
-  @pollingOperation(Widgets.getWidgetOperationStatus)
+  @pollingOperation(Widgets.getWidgetDeleteOperationStatus)
   deleteWidget is Operations.LongRunningResourceDelete<Widget>;
 
   @doc("List Widget resources.")