fix: remove unnecessary whitespace in Snowberry_AppendMediatorTests

Author: VNNCC

src/Snowberry.Mediator.Tests/Snowberry_AppendMediatorTests.cs

@@ -1006,7 +1006,7 @@ public async Task Test_AppendHandlers_ConcurrentPluginLoading()
 
         // IMPORTANT: Snapshot the executions ONCE
         var executions = NotificationHandlerExecutionTracker.GetExecutions();
-        
+
         // Verify all handlers executed
         Assert.Equal(3, executions.Count);
         Assert.Contains(nameof(CorePluginHandler), executions);