[Bug]: Target Query not Used (#2233)

🐛 (WorkItemMigrationContext.cs): fix variable name from
_config.WIQLQuery to targetWIQLQuery

The variable name _config.WIQLQuery is incorrect and should be
targetWIQLQuery to match the intended logic and improve code
readability. This change ensures that the correct query is used for
filtering existing work items, preventing potential migration issues.

Fixes: #2232

src/VstsSyncMigrator.Core/Execution/MigrationContext/WorkItemMigrationContext.cs

@@ -212,7 +212,7 @@ protected override void InternalExecute()
                         Engine.Source.WorkItems.Project.Name, Engine.Target.WorkItems.Project.Name, contextLog);
 
                     sourceWorkItems = ((TfsWorkItemMigrationClient)Engine.Target.WorkItems).FilterExistingWorkItems(
-                        sourceWorkItems, _config.WIQLQuery,
+                        sourceWorkItems, targetWIQLQuery,
                         (TfsWorkItemMigrationClient)Engine.Source.WorkItems);
                     contextLog.Information(
                         "!! After removing all found work items there are {SourceWorkItemCount} remaining to be migrated.",