svx a11y: Avoid querying for XComponent iface

In SvxGraphCtrlAccessibleContext::disposing, use a reference
to the concrete accessibility::AccessibleShape instead of
the abstract XAccessible UNO interface from the start, which
drops the need to explicitly query for the XComponent interface.

Change-Id: I943c03ecbf801b3fff0592996ce3d0af352cd3d0
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/211186
Reviewed-by: Michael Weghorn <m.weghorn@posteo.de>
Tested-by: Jenkins

svx/source/accessibility/GraphCtlAccessibleContext.cxx

@@ -460,10 +460,9 @@ void SAL_CALL SvxGraphCtrlAccessibleContext::disposing()
     {
         for (const auto& rEntry : mxShapes)
         {
-            rtl::Reference<XAccessible> pAcc(rEntry.second);
-            Reference< XComponent > xComp( pAcc.get(), UNO_QUERY );
-            if( xComp.is() )
-                xComp->dispose();
+            rtl::Reference<::accessibility::AccessibleShape> pAcc(rEntry.second);
+            if (pAcc.is())
+                pAcc->dispose();
         }
 
         mxShapes.clear();