This fixes wrong display (random days could have been shown marked) when not
using wxCAL_SHOW_HOLIDAYS style. Apparently we need to set the marks
unconditionally as they are not turned off by default, so ensure we call
UpdateMarks() even without wxCAL_SHOW_HOLIDAYS.
See #13934.
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@70567 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775