Remove hard limit on number of pages in wxHtmlPrintout.

Remove hard limit on number of pages in wxHtmlPrintout.

This seems to be a leftover from an old version in which the page breaks
positions were stored in a fixed size array. As the code uses a dynamic array
now there doesn't seem to be any reason to impose any limit on the number of
pages and some people did run into the old 999 pages limitation apparently.

Closes #11159.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@65076 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775