Don't adjust menu item positions for title for menubar menus in wxMSW.

Don't adjust menu item positions for title for menubar menus in wxMSW.

The code in wxMSW menu code which accounted for the extra items used to show
popup menu title has become incorrect since the changes of r66178 as now the
non-popup menus have titles as well.

Correct the check to only do the adjustment for the popup menus.

Closes #12922.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@66845 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775