[API CHANGE] MediaProperties don't accept GraphicObject URL anymore

This changes the description for URL property as it doesn't
support GraphicObject URL (vnd.sun.star.GraphicObject) anymore
so not a direct API change, but it is a significant functional
change.

Change-Id: Ie440d2140274243733a18ebc18089d2daa820c74
Reviewed-on: https://gerrit.libreoffice.org/53243Reviewed-by: Tomaž Vajngerl <quikee@gmail.com>
Tested-by: Tomaž Vajngerl <quikee@gmail.com>

offapi/com/sun/star/graphic/MediaProperties.idl

@@ -42,15 +42,18 @@ published service MediaProperties
         <p>In addition to the normal protocols like file:// or http://
         you can use private URLs as follows to get access to graphics
         lying inside the graphicrepository system within an Office context:
-
         <ul>
             <li><code>private:graphicrepository/<em>&lt;path_in_repository&gt;</em></code></li>
         </ul>
-And additionally, GraphicObject scheme URLs like
-            <ul> <li>vnd.sun.star.GraphicObject:10000000000001940000012FB99807BD</li> </ul>
-              can be used to access graphics held by the GraphicCache implementation.
         </p>
-</p>
+
+        <p>
+        Note: As of LibreOffice 6.1 GraphicObject scheme URLs are not supported anymore.
+        For example:
+        <ul>
+            <li>vnd.sun.star.GraphicObject:10000000000001940000012FB99807BD</li>
+        </ul>
+        </p>
     */
     [optional, property ] string URL;