remove unused imports

Author: anshooarora

ExtentReports.Tests/Service/ExtentTestManager.cs

@@ -1,12 +1,5 @@
-using NUnit.Framework;
-using System;
-using System.Collections.Generic;
-using System.Diagnostics;
-using System.Linq;
-using System.Runtime.CompilerServices;
-using System.Text;
+using System.Collections.Generic;
 using System.Threading;
-using System.Threading.Tasks;
 
 namespace AventStack.ExtentReports.Tests.Parallel
 {