remove NotifyOfCrossThreadDependency call

when a debugger is attached, NotifyOfCrossThreadDependency will freeze the thread to send notification to the debugger. Because this NoMessagePumpSynchronizationContext is heavily used, including nested inside code holding the JTF lock, this leads the process being debugged becomes extremely slow when JTF is heavily used.

Author: Lifeng Lu

src/Microsoft.VisualStudio.Threading/JoinableTaskContext.cs

@@ -302,11 +302,6 @@ protected internal virtual SynchronizationContext NoMessagePumpSynchronizationCo
     {
         get
         {
-            // Callers of this method are about to take a private lock, which tends
-            // to cause a deadlock while debugging because of lock contention with the
-            // debugger's expression evaluator. So prevent that.
-            Debugger.NotifyOfCrossThreadDependency();
-
             return NoMessagePumpSyncContext.Default;
         }
     }