Update the remarks according to the current behavior (dotnet#8738)

The exception escalation policy terminates by default the process only on the .NET Framework 4.0. From the .NET Framework 4.5 onwards the default behavior is to keep the process alive. The remarks should be updated to reflect the current policy.

Author: theodorzoulias

xml/System.Threading.Tasks/UnobservedTaskExceptionEventArgs.xml

@@ -51,7 +51,7 @@
       <format type="text/markdown"><![CDATA[  
   
 ## Remarks  
- The Exception property is used to examine the exception without marking it as observed, whereas the <xref:System.Threading.Tasks.UnobservedTaskExceptionEventArgs.SetObserved%2A> method is used to mark the exception as observed. Marking the exception as observed prevents it from triggering exception escalation policy which, by default, terminates the process.  
+ The Exception property is used to examine the exception without marking it as observed, whereas the <xref:System.Threading.Tasks.UnobservedTaskExceptionEventArgs.SetObserved%2A> method is used to mark the exception as observed. Marking the exception as observed prevents it from triggering exception escalation policy. For more information, see the [Remarks](/dotnet/api/system.threading.tasks.taskscheduler.unobservedtaskexception#remarks) of the <see cref="E:System.System.Threading.Tasks.TaskScheduler.UnobservedTaskException" /> event.  
   
  ]]></format>
     </remarks>