Port documentation improvements from dotnet/runtime#121232 (#11998)

* Port documentation improvements from runtime PR #121232

Updated ObjectiveCMarshal.CreateReferenceTrackingHandle documentation:
- Changed "The Initialize()" to use proper xref to Initialize method
- Changed "The `obj`" to "The `obj` parameter" for clarity

Co-authored-by: jkotas <6668460+jkotas@users.noreply.github.com>

* Update xml/System.Runtime.InteropServices.ObjectiveC/ObjectiveCMarshal.xml

* Update xml/System.Runtime.InteropServices.ObjectiveC/ObjectiveCMarshal.xml

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: jkotas <6668460+jkotas@users.noreply.github.com>
Co-authored-by: Jan Kotas <jkotas@microsoft.com>

Author: Copilot

xml/System.Runtime.InteropServices.ObjectiveC/ObjectiveCMarshal.xml

@@ -72,9 +72,9 @@
 
 ## Remarks
 
-The Initialize() must be called prior to calling this function.
+The <xref:System.Runtime.InteropServices.ObjectiveC.ObjectiveCMarshal.Initialize*> function must be called prior to calling this function.
             
-The `obj` must have a type in its hierarchy marked with
+The `obj` parameter must have a type in its hierarchy marked with
 <xref:System.Runtime.InteropServices.ObjectiveC.ObjectiveCTrackedTypeAttribute>.
 
 The "Is Referenced" callback passed to Initialize()