ProcessStartInfo.CreateNoWindow does not work on Unix-like platforms (dotnet#33)

See https://github.com/dotnet/corefx/issues/26337 and
https://github.com/dotnet/corefx/issues/28182.

Author: omajid

xml/System.Diagnostics/ProcessStartInfo.xml

@@ -306,6 +306,8 @@
   
 ## Remarks  
  If the <xref:System.Diagnostics.ProcessStartInfo.UseShellExecute%2A> property is `true` or the <xref:System.Diagnostics.ProcessStartInfo.UserName%2A> and <xref:System.Diagnostics.ProcessStartInfo.Password%2A> properties are not `null`, the <xref:System.Diagnostics.ProcessStartInfo.CreateNoWindow%2A> property value is ignored and a new window is created.  
+
+ .NET Core does not support creating windows directly on Unix-like platforms, including macOS and Linux. This property is ignored on such platforms.
   
    
   
@@ -1498,4 +1500,4 @@ p.WaitForExit();
       </Docs>
     </Member>
   </Members>
-</Type>
+</Type>