Clarify DllImport assembly name support that is only in .NET Framework (dotnet#8775)

Author: elinor-fung

xml/System.Runtime.InteropServices/DllImportAttribute.xml

@@ -124,13 +124,13 @@
         <Parameter Name="dllName" Type="System.String" />
       </Parameters>
       <Docs>
-        <param name="dllName">The name of the DLL that contains the unmanaged method. This can include an assembly display name, if the DLL is included in an assembly.</param>
+        <param name="dllName">The name of the DLL that contains the unmanaged method. In .NET Framework, this can include an assembly display name, if the DLL is included in an assembly.</param>
         <summary>Initializes a new instance of the <see cref="T:System.Runtime.InteropServices.DllImportAttribute" /> class with the name of the DLL containing the method to import.</summary>
         <remarks>
           <format type="text/markdown"><![CDATA[  
   
 ## Remarks  
- If an unmanaged DLL file is included in an assembly, for example, by using the linker or the `/linkresource` compiler option, you can specify the assembly display name as part of `dllName`. For example, if an unmanaged DLL named `unmanaged.dll` is included in a managed assembly named `MyAssembly`, the attribute might be specified as shown in the following code.  
+ **.NET Framework only:** If an unmanaged DLL file is included in an assembly, for example, by using the linker or the `/linkresource` compiler option, you can specify the assembly display name as part of `dllName`. For example, if an unmanaged DLL named `unmanaged.dll` is included in a managed assembly named `MyAssembly`, the attribute might be specified as shown in the following code.
   
  :::code language="cpp" source="~/snippets/cpp/VS_Snippets_CLR_System/system.runtime.interopservices.dllimportattribute/cpp/source.cpp" id="Snippet2":::
  :::code language="csharp" source="~/snippets/csharp/System.Runtime.InteropServices/DllImportAttribute/.ctor/source.cs" id="Snippet2":::