Update GC.AllocateArray documentation (#10142)

Author: jkotas

xml/System/GC.xml

@@ -200,7 +200,7 @@ The following example uses several GC methods to get generation and memory infor
 
 ## Remarks
 
-If pinned is set to `true`, `T` must not be a reference type or a type that contains object references.
+In .NET 7 and earlier versions: If pinned is set to `true`, `T` must not be a reference type or a type that contains object references.
 
           ]]></format>
         </remarks>
@@ -255,7 +255,7 @@ If pinned is set to `true`, `T` must not be a reference type or a type that cont
 
 ## Remarks
 
-If pinned is set to `true`, `T` must not be a reference type or a type that contains object references.
+In .NET 7 and earlier versions: If pinned is set to `true`, `T` must not be a reference type or a type that contains object references.
 
 Skipping zero-initialization is a security risk. The uninitialized array can contain invalid valuetype instances or sensitive information created by other parts of the application.
 The code operating on uninitialized arrays should be heavily scrutinized to ensure that the uninitialized data is never read.