Remove outdated comment (#3545)

* Remove outdated comment

We added `Thread.Abort()` to .NET Core 2.0/.NET Standard 2.0. We should remove this comment because it's misleading. It's still a bad API, but it's there.

* readd new line

Author: Immo Landwerth

xml/System.Threading/Thread.xml

@@ -517,9 +517,7 @@ Main thread: ThreadProc.Join has returned.  Press Enter to end program.
 ## Remarks  
   
 > [!IMPORTANT]
-> The `Thread.Abort` method should be used with caution. Particularly when you call it to abort a thread other than the current thread, you do not know what code has executed or failed to execute when the <xref:System.Threading.ThreadAbortException> is thrown, nor can you be certain of the state of your application or any application and user state that it is responsible for preserving. For example, calling `Thread.Abort` may prevent static constructors from executing or prevent the release of unmanaged resources. 
->
-> Note that the `Thread.Abort` method is not supported on .NET Core.
+> The `Thread.Abort` method should be used with caution. Particularly when you call it to abort a thread other than the current thread, you do not know what code has executed or failed to execute when the <xref:System.Threading.ThreadAbortException> is thrown, nor can you be certain of the state of your application or any application and user state that it is responsible for preserving. For example, calling `Thread.Abort` may prevent static constructors from executing or prevent the release of unmanaged resources
 
        ]]></format>
         </remarks>