Update the doc for System.Diagnostics.Process (#9624)

Author: yahoo0742

xml/System.Diagnostics/Process.xml

@@ -110,6 +110,12 @@
 
  A system process is uniquely identified on the system by its process identifier. Like many Windows resources, a process is also identified by its handle, which might not be unique on the computer. A handle is the generic term for an identifier of a resource. The operating system persists the process handle, which is accessed through the <xref:System.Diagnostics.Process.Handle%2A> property of the <xref:System.Diagnostics.Process> component, even when the process has exited. Thus, you can get the process's administrative information, such as the <xref:System.Diagnostics.Process.ExitCode%2A> (usually either zero for success or a nonzero error code) and the <xref:System.Diagnostics.Process.ExitTime%2A>. Handles are an extremely valuable resource, so leaking handles is more virulent than leaking memory.
 
+On macOS, the following properties return 0:
+
+ - <xref:System.Diagnostics.Process.PeakVirtualMemorySize64>
+ - <xref:System.Diagnostics.Process.PrivateMemorySize64>
+ - <xref:System.Diagnostics.Process.PeakWorkingSet64>
+
 > [!NOTE]
 >  This class contains a link demand and an inheritance demand at the class level that applies to all members. A <xref:System.Security.SecurityException> is thrown when either the immediate caller or the derived class does not have full-trust permission. For details about security demands, see [Link Demands](/dotnet/framework/misc/link-demands).