Remove unused usings from AnalysisService.cs

Author: Kapil Borle

src/PowerShellEditorServices/Analysis/AnalysisService.cs

@@ -7,7 +7,6 @@
 using System;
 using System.Linq;
 using System.Management.Automation.Runspaces;
-using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.PowerShell.EditorServices.Console;
 using System.Management.Automation;