Fix content.integration tests warnings (#17817)

Co-authored-by: metalgearsloth <31366439+metalgearsloth@users.noreply.github.com>

Content.IntegrationTests/PoolManagerTestEventHandler.cs

@@ -1,7 +1,4 @@
-using System;
-using System.Threading.Tasks;
-using NUnit.Framework;
-
+
 [assembly: Parallelizable(ParallelScope.Children)]
 
 namespace Content.IntegrationTests;