Improve calculation of wxComboCtrl best size which doesn't work correctly for non-default fonts as shown by r72935. It is still not perfect but better now. Closes #14825. git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@72955 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775