Update GCHandle.xml (#3169)

* Update GCHandle.xml

Incorporate feedback from https://github.com/dotnet/coreclr/issues/26658#issuecomment-530487407

* Update xml/System.Runtime.InteropServices/GCHandle.xml

Co-Authored-By: Ron Petrusha <[email protected]>

* Update xml/System.Runtime.InteropServices/GCHandle.xml

Co-Authored-By: Ron Petrusha <[email protected]>

* Update xml/System.Runtime.InteropServices/GCHandle.xml

Co-Authored-By: Ron Petrusha <[email protected]>

Author: jkotas

xml/System.Runtime.InteropServices/GCHandle.xml

@@ -107,13 +107,15 @@
       </ReturnValue>
       <Parameters />
       <Docs>
-        <summary>Retrieves the address of an object in a <see cref="F:System.Runtime.InteropServices.GCHandleType.Pinned" /> handle.</summary>
-        <returns>The address of the pinned object as an <see cref="T:System.IntPtr" />.</returns>
+        <summary>Retrieves the address of object data in a <see cref="F:System.Runtime.InteropServices.GCHandleType.Pinned" /> handle.</summary>
+        <returns>The address of the pinned data object.</returns>
         <remarks>
           <format type="text/markdown"><![CDATA[  
   
 ## Remarks  
- This method is used to get a stable pointer to the object. Pinning an object prevents the garbage collector from moving it around in memory, thereby reducing the efficiency of the garbage collector.  
+ This method is used to get a stable pointer to the object data. For arrays, this method returns the address of the first element. For strings, this method returns the address of the first character. 
+ 
+ Pinning an object prevents the garbage collector from moving it around in memory, thereby reducing the efficiency of the garbage collector.  
   
  ]]></format>
         </remarks>