Update Task.xml (dotnet#8609)

Added link to "Task-based asynchronous pattern (TAP) in .NET: Introduction and overview" in the "See Also" section

Author: vcrobe

xml/System.Threading.Tasks/Task.xml

@@ -173,6 +173,7 @@
     <threadsafe>All members of <see cref="T:System.Threading.Tasks.Task" />, except for <see cref="M:System.Threading.Tasks.Task.Dispose" />, are thread-safe and may be used from multiple threads concurrently.</threadsafe>
     <altmember cref="T:System.Threading.Tasks.Task`1" />
     <related type="Article" href="/dotnet/standard/parallel-programming/task-parallel-library-tpl">Task Parallel Library (TPL)</related>
+    <related type="Article" href="/dotnet/standard/asynchronous-programming-patterns/task-based-asynchronous-pattern-tap">Task-based asynchronous pattern (TAP) in .NET: Introduction and overview</related>
     <related type="Article" href="/dotnet/standard/parallel-programming/task-based-asynchronous-programming">Task-based Asynchronous Programming</related>
     <related type="ExternalDocumentation" href="https://aka.ms/dotnet-parallel-samples">Samples for Parallel Programming with the .NET Core and .NET Standard</related>
   </Docs>